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Equipment Discussions >> Reflectors

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Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

First Light On My 20" f/3 Lockwood/JP Astrocraft
      #5529511 - 11/20/12 07:25 AM Attachment (873 downloads)

It is amazing how time flies when you order a new telescope. At first is creeps and then later, it slips from your day-to-day consciousness and suddendly it is found to be nearing completion. This has been the case with my 20" f/3 Lockwood/JP Astrocraft scope. In about 3 weeks, it will have gone through the final completion stage.

We did however get first light in Central Illinois this past weekend when I went up to look at the progress and provide further input into some of the design features. It is so feature laden for visual, astrovideo, binoviewing and DSLR applications that I will save that for another post.

The scope has a Lockwood 20" 1.25" thick Pyrex f/3 primary coupled with a 5" m.a. Lockwood secondary. The JPA custom mirror cell was tested by Lockwood under various bench conditions with the unfinished primary and has been optomized for the thin mirror to operate in all positions. The mirror cell is a work of art all by itself with the use of spherical bearings on each triangle and roller bearings on the lower mirror edge supports. Views of Jupiter's GRS and surrounding ovals at 219x under less than ideal conditions still showed very detailed and colorful images. The unfinished podium on the non-viewing side includes wired and wireless handpands, 12" ultrabook computer, power supplies for the computer and eventually a heated shield that will prevent the computer screen from dewing up. All wiring is internally routed and the entire scope will be powered by one external 12v wire going into the powered ground board.

Mike Lockwood, the optician on this project, is a former electrical engineer/research scientist/ATM that went into the optical business and is building what are arguably some of the finest and most consistent sub f/4 optics on the planet in sizes up to 60" and f ratios as fast as f/2 (he recommends no faster than f/2.75 for Newtonians and I have viewed through one of his 28" f/2.75's that was an absolute stunner). John Pratte, the scope builder, is a chemical engineer, manufacturing executive, former world champion NHRA car tuner/builder, optician, machinist and all around nice guy.

I have included a picture that Mike Lockwood took this weekend as we all experienced a group first light.

Edited by Bob S. (11/20/12 02:04 PM)


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tezster
scholastic sledgehammer
*****

Reged: 07/14/09

Loc: Missisauga, Canada
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5529576 - 11/20/12 08:23 AM

That is one FINE looking scope! It's hard to imagine it has the same FL as a 10" F6 - comfy seated observing with feet on the ground all the way to the zenith

Mind if I ask what the maximum EP height is?


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Happy Birthday JayinUTModerator
I'm not Sleepy
*****

Reged: 09/19/08

Loc: Utah
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: tezster]
      #5529599 - 11/20/12 08:42 AM

Beautiful scope! Oh the views you are going to have!

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Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: tezster]
      #5529620 - 11/20/12 09:02 AM

Quote:

That is one FINE looking scope! It's hard to imagine it has the same FL as a 10" F6 - comfy seated observing with feet on the ground all the way to the zenith

Mind if I ask what the maximum EP height is?




Maximum ep height is 62" at zenith. John Pratte had to add height to the rocker box feet and make a slightly taller rocker box to get the desired height that I wanted.

Edited by Bob S. (11/20/12 09:02 AM)


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Darren Drake
Carpal Tunnel
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Reged: 10/09/02

Loc: Chicagoland
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: JayinUT]
      #5529625 - 11/20/12 09:07 AM

Very nice! What is that thingy above the focuser? It looks like another focuser.....

Edited by Darren Drake (11/20/12 09:08 AM)


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Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Darren Drake]
      #5529632 - 11/20/12 09:09 AM

Quote:

Very nice! What is that thingy abouve the focuser? It looks like another focuser.....



You can never have enough focusers Actually it is a 1.25"-2" holster for placement of my Mallincam when it is out of the focuser. The 1.25" portion of the holder is a Baader Clic-Lock device that requires just a slight turn of the knurled nob to secure the camera. You are also probably wondering about the turnbuckle on the front of the rockerbox/mirror box. That is used in conjunction with two sliding bolts on the rear of the mirror box that go into the rocker box to place it in an upright position to simply lean the telescope over and wheel it out to my observing site. The axles have quick release pins that allow the wheels to come off and the axle to be removed. However, you can observe with the wheels attached.


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cliff mygatt
Carpal Tunnel


Reged: 01/27/09

Loc: Kitsap County, WA
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5529655 - 11/20/12 09:29 AM

It is a lovely scope combined with great optics, one cannot go wrong. Looking forward to see some of those mallincam photos. Good Luck!

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Busguy
member


Reged: 06/14/07

Loc: Kentucky
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: cliff mygatt]
      #5530279 - 11/20/12 02:16 PM

What a beautiful scope. Craftsmanship looks superb.

Enjoy many nights with it.

Joe


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killdabuddha
Pooh-Bah
*****

Reged: 08/26/11

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Busguy]
      #5530358 - 11/20/12 02:53 PM

Wow. And how in the world did you get those angle-fitted tube-plug mounting plates?

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JimMo
I'd Rather Do It Myself


Reged: 01/08/07

Loc: Under the SE Michigan lightdom...
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5530359 - 11/20/12 02:53 PM

Awesome telescope Bob. I'm sure you'll be thrilled with the views.

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auriga
Pooh-Bah


Reged: 03/02/06

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5530623 - 11/20/12 04:57 PM

Bob,
Congratulations, a superb scope! You will find it easy and enjoyable to use.

I am not at all surprised at how good it is, since I have the 16"f/4 version, the "sweet sixteen' pictured on John Pratte's web site. It's a beauty and a great pleasure to use. I have had no trouble with it at all. Easy to collimate, retains object when I change eyepieces, moves easily but stays where I put it. Very solid construction, very rigid, goes together easily and disassembles easily. I have a Wessling mirror, one of the last ones he made rather than a Lockwood but I think they would be equivalent. I notice you have chosen the same wood stain I did. Looks great.

Let us know your experiences with the 20" f/3 once it is delivered and you have a chance to do some more observing with it. You are one of the most experienced posters with a variety of scopes so it will be good to hear your take on this one.

Bill Meyers


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Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: auriga]
      #5530745 - 11/20/12 06:13 PM

Quote:

Bob,
Congratulations, a superb scope! You will find it easy and enjoyable to use.

I am not at all surprised at how good it is, since I have the 16"f/4 version, the "sweet sixteen' pictured on John Pratte's web site. It's a beauty and a great pleasure to use. I have had no trouble with it at all. Easy to collimate, retains object when I change eyepieces, moves easily but stays where I put it. Very solid construction, very rigid, goes together easily and disassembles easily. I have a Wessling mirror, one of the last ones he made rather than a Lockwood but I think they would be equivalent. I notice you have chosen the same wood stain I did. Looks great.

Let us know your experiences with the 20" f/3 once it is delivered and you have a chance to do some more observing with it. You are one of the most experienced posters with a variety of scopes so it will be good to hear your take on this one.

Bill Meyers




Thanks Bill. I too had a 18" f/4.5 Wessling mirror in a beautiful structure whos name escapes me for the moment. It was an absolutely superb mirror. Dick was one of the handful of very good opticians. John Pratte has some of his mirrors and at least one or two for sale I think.

John as you know has been absolutely wonderful to work with. He is extremely meticulous and thinks things through before charging ahead. I could not ask for a better build.
Bob


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Mike Lockwood
Vendor, Lockwood Custom Optics
*****

Reged: 10/01/07

Loc: Usually in my optical shop
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: killdabuddha]
      #5530774 - 11/20/12 06:31 PM

Quote:

Wow. And how in the world did you get those angle-fitted tube-plug mounting plates?



Well, John made them, of course.

While using this scope, I found myself repeatedly asking for the observing chair - my back was hurting from having to stoop over at the eyepiece of what is very clearly a telescope that should be used while seated.


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Jarad
Postmaster
*****

Reged: 04/28/03

Loc: Atlanta, GA
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Mike Lockwood]
      #5530946 - 11/20/12 08:06 PM

Glad to see it finally arrived, Bob! I'm sure you'll enjoy it under those nice steady Florida skies.

Be sure to bring it to PSSG next year!

Jarad


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Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Jarad]
      #5530993 - 11/20/12 08:38 PM Attachment (250 downloads)

Quote:

Glad to see it finally arrived, Bob! I'm sure you'll enjoy it under those nice steady Florida skies.

Be sure to bring it to PSSG next year!

Jarad




Jarad, It has not "arrived" yet but is getting within three weeks of arrival.

Here is a picture of the custom-machined billet aluminum offset spider hub, collimation screws, tilt plate and vanes that John Pratte manufactured. You will also notice that the UTA has two flat sides that allow it to nest better in the mirror box if that is desired.

You will also notice that the spider vanes are indeed parallel (opposing vanes) and perpendicular (neighboring
vanes), but they are not coincident, or on the same line.

The purpose of this vane's orientation was to prevent the 5" secondary from experiencing rotational torque generally associated with larger secondaries. You see people using wheel weights to prevent the rotation. John Pratte as an engineer (with the concurrence of Mike Lockwood) couldn't live with that and made them so there is virtually no rotational torquing of the secondary. The diffraction spikes are just four but behave a bit differently when you defocus on a star seperating in a horizontal fashion. The spider vanes also have their own dedicated uprights on the UTA that are primary support for the vanes and secondarily for the UTA rings that have other supports. The vertical slots in the billet center hub are reportedly for receiving transmissions from outer space. I am thinking of also using this as a SETI instrument

Edited by Bob S. (11/20/12 09:06 PM)


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mtb54703
professor emeritus
*****

Reged: 11/12/08

Loc: Eau Claire, WI
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5531870 - 11/21/12 10:20 AM

Quote:


The purpose of this vane's orientation was to prevent the 5" secondary from experiencing rotational torque generally associated with larger secondaries.




Interesting... It's not just that its a larger secondary, it's the greater secondary offset that's required for a faster mirror that is responsible for the greater rotational torque...



Awesomely nice looking scope!


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jim molinari
member
*****

Reged: 02/02/08

Loc: California
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5532428 - 11/21/12 02:54 PM

Bob ...
Very well thought out with top quality optics and structure. I like your Watec Monitor and Mallincam mount ... clever! I will be interested to hear how the cooling/airflow system performs. I hope you get a chance to bring it out West where I can see it in action. Congrats and enjoy!
Jim


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Jarad
Postmaster
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Reged: 04/28/03

Loc: Atlanta, GA
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5532454 - 11/21/12 03:12 PM

Quote:

Jarad, It has not "arrived" yet but is getting within three weeks of arrival.




Hey, no fair! You can't title your thread "First light" until you get the scope and get first light!

Now I can't be jealous for 3 more weeks!

Jarad


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David Castillo
Carpal Tunnel
*****

Reged: 09/09/06

Loc: Carmel Valley, Ca
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Jarad]
      #5532499 - 11/21/12 03:33 PM

Looks like the best thing to cure a back ache.
----
Dave


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Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: jim molinari]
      #5532572 - 11/21/12 04:13 PM

Quote:

Bob ...
Very well thought out with top quality optics and structure. I like your Watec Monitor and Mallincam mount ... clever! I will be interested to hear how the cooling/airflow system performs. I hope you get a chance to bring it out West where I can see it in action. Congrats and enjoy!
Jim




Jim, The cooling system is a combination of proven technologies used by two different astronomers and many others I am sure. BTW, we sure had some beautiful views through your 20" scope, Chris Ford's 24" and Nick Tsakoyias TEC 180 FL scope at the Golden State Star Party this year. Joe Wambo with his 32" f/3.7 Lockwood/Webster placed a fan above his primary mirror scrubing off the boundary layer. I also talked with Jimmy Lowery who has a 48" f/4 telescope out in Texas and we were discussing cooling strategies for mirrors and he mentioned that he uses 10 Maglev (magnetic levitation) fans in an enclosed rear mirror cell for his behemoth scope.

What John Pratte operationalized was an enclosure for the rear of the telescope that has at the center a Maglev fan (the fans are inherently more vibration free than a conventional motored fan) mounted in Sorbothane and fastened with a sandwiched support plate to the rear aluminum enclosed back. The fan has a potentiometer to control fan speed/air flow and there is an annulus above the primary that creates a venturi effect that sucks the air off the mirror face and out the back of the scope. On the front of the mirror about a foot above the primary will be a smaller Maglev fan suspended by thin but sturdy wires that will also be a variable speed device and blow air away from the center of the mirror. The fan will be able to rotate out of the way to collimate the scope.

The combination of the blowing/sucking system we have termed the Comprehensive Boundary Layer Mitigation System or CBLMS for short. The CBLMS should accomplish several things: 1. It should scrub the boundary layer off the surface of the primary 2. It should provide for more rapid equilibration of the primary and uniformally accomplish this with the combined fan systems. Again, these technologies have been used seperately but to my knowledge not quite in the way that we are going about it.

In Joe Wambo's scope at this years Winter Star Party in the Florida Keys, we were looking at Mars at 950x with "etched" views of the Martian atmosphere and planets surface. We could see very distinctly defined clouds above the Martian surface. Now, my little 20" will not produce those kind of views with eyepieces but it sure will with my Mallincam Extreme astrovideo camera. Bob

Edited by Bob S. (11/21/12 07:27 PM)


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Project Galileo
scholastic sledgehammer
*****

Reged: 11/14/07

Loc: Jefferson County, Colorado
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5532699 - 11/21/12 05:28 PM

Beautiful. Just beautiful. Congrats!

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auriga
Pooh-Bah


Reged: 03/02/06

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5532788 - 11/21/12 06:35 PM

Bob,
I am interested to see that you have adopted the Dick Wessling/John Pratte/Ross Sackett wheel arrangement, which I have found to be excellent on my scope.

See:
http://stardazed.com/CaptainNemo.html

and jpastrocraft.com

Jon Isaacs has used this design as well.

I too have found that John Pratte is an excellent person to work with, as well as being a fine craftsman with the insight of an engineer.

Bill


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Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: auriga]
      #5532806 - 11/21/12 06:50 PM

Quote:

Bob,
I am interested to see that you have adopted the Dick Wessling/John Pratte/Ross Sackett wheel arrangement, which I have found to be excellent on my scope.

See:
http://stardazed.com/CaptainNemo.html

and jpastrocraft.com

Jon Isaacs has used this design as well.

I too have found that John Pratte is an excellent person to work with, as well as being a fine craftsman with the insight of an engineer.

Bill




Bill, It is neat how scope builders stand on the shoulders of those that came before them. John Pratte is also integrating the axle/tires on the front of the rocker box to work with supplied wheelbarrow handles so that I can roll the scope up a ramp if I choose to. Bob


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Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5544196 - 11/28/12 04:44 PM Attachment (137 downloads)

Well, progress continues on the JPA. As part of the CBLMS (Comprehensive Boundary Layer Mitigation System), John Pratte has been doing his engineering homework to produce the frontal magnetic levitation fan that will be hidden in the shadow of the secondary mirror and blow on the primary. I have included a couple of pictures of this work in progress that will be suspended by very thin 12v current conducting wires.

Edited by Bob S. (11/28/12 06:13 PM)


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Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5544203 - 11/28/12 04:47 PM Attachment (132 downloads)

Here is a picture of the forward fan in the up position so that I will be able to collimate the telescope. We are also considering the placement of the wires to add as little diffraction spike input as possible. You will notice that the ring is not round. It mimics the .42" offset of the secondary mirror.

Edited by Bob S. (11/28/12 04:48 PM)


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Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5544313 - 11/28/12 06:00 PM Attachment (101 downloads)

This is a picture of the ring over the schematic of the secondary unit and spider and note the rings connect points coincide with the vanes coming out of the central hub. Because the vanes are not coincident, it provides a bit of a challenge in terms of diffraction issues.

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Mike Lockwood
Vendor, Lockwood Custom Optics
*****

Reged: 10/01/07

Loc: Usually in my optical shop
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5544326 - 11/28/12 06:11 PM

Quote:

Here is a picture of the forward fan in the up position so that I will be able to collimate the telescope. We are also considering the placement of the wires to add as little diffraction spike input as possible. You will notice that the ring is not round. It mimics the .42" offset of the secondary mirror.



Wow, first we had the flip phone, now we have the flip fan.

These really do work well, even on up to a 32" scope, maybe larger.


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nsldvd
sage


Reged: 10/02/08

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5544451 - 11/28/12 07:53 PM Attachment (77 downloads)

Quote:

This is a picture of the ring over the schematic of the secondary unit and spider and note the rings connect points coincide with the vanes coming out of the central hub. Because the vanes are not coincident, it provides a bit of a challenge in terms of diffraction issues.




Not sure the fan thing is so complicated but good luck and I'm sure it'll work out fine for you...


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Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: nsldvd]
      #5544483 - 11/28/12 08:14 PM

Quote:

Quote:

This is a picture of the ring over the schematic of the secondary unit and spider and note the rings connect points coincide with the vanes coming out of the central hub. Because the vanes are not coincident, it provides a bit of a challenge in terms of diffraction issues.




Not sure the fan thing is so complicated but good luck and I'm sure it'll work out fine for you...




On your 32" Webster, the spider vanes are perpendicular. Mine are only perpendicular to each pair neighboring each other. How do you remove your fan for collimation and what gauge/strand count wire did you use?


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nsldvd
sage


Reged: 10/02/08

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5544494 - 11/28/12 08:24 PM Attachment (74 downloads)

Quote:

On your 32" Webster, the spider vanes are perpendicular.



Hi Bob,
I'll get back to you...


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Howie Glatter
Vendor


Reged: 07/04/06

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5544522 - 11/28/12 08:50 PM

Bob, your vanes are perpendicular (at right angles to eachother). They are just not co-linear ; they don't form an X, crossing in the center. Dave's Webster also looks just a little offset (not crossing the center) in his photo.

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Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Howie Glatter]
      #5544529 - 11/28/12 08:53 PM

Howie, "co-linear". That is a new catchy buzz word to drop at a cocktail party. I think the spelling is "collinear". It is a shame that I gave up drinking<g>. In Albert Highe's new book ( Engineering, Design and Construction of Portable Newtonian Telescopes 2012) on page 509 he describes his and my spider vanes as "Opposing vanes are not coplaner. However, the angle between adjacent vanes is 90 degrees, making opposing vanes parallel". Now I have two buzz words for that elusive cocktail party. Guess I am going to have to brush up on my geometry skills if I drop those into the conversation. Bob

Edited by Bob S. (11/29/12 06:56 AM)


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nsldvd
sage


Reged: 10/02/08

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5547729 - 11/30/12 07:22 PM Attachment (83 downloads)

Quote:

Quote:

Quote:

This is a picture of the ring over the schematic of the secondary unit and spider and note the rings connect points coincide with the vanes coming out of the central hub. Because the vanes are not coincident, it provides a bit of a challenge in terms of diffraction issues.




Not sure the fan thing is so complicated but good luck and I'm sure it'll work out fine for you...




On your 32" Webster, the spider vanes are perpendicular. Mine are only perpendicular to each pair neighboring each other. How do you remove your fan for collimation and what gauge/strand count wire did you use?




Hi Bob,
Thanks for your PM and best of hopes with your new scope. With your permission...
I think you're on to something with the boundary layer fan. It may have been about 10 yrs back when I put a similar fan on my 25" Obsession and wired a switch on the UTA that turned the fan "On" and "Off". I recall Sirius in the EP and with the fan off and the mirror only about 60% ambient I could see the star somewhat fuzzy. When I flipped the switch Sirius cleaned up dramatically. Later in the evening when the mirror was more like 85%-95% ambient I repeated the test/experiment but was unable to detect the same or similar result. Over several observing events it became clear the boundary fan was most useful in the early evening and in the later observing period could be turned off and save some battery power. Not every scope needs this type of fan but it does seem to bring the desired observing objective sooner than later. Below is a photo of my old Obsession showing the fan...


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nsldvd
sage


Reged: 10/02/08

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5547743 - 11/30/12 07:30 PM Attachment (66 downloads)

Quote:

Quote:

Quote:

This is a picture of the ring over the schematic of the secondary unit and spider and note the rings connect points coincide with the vanes coming out of the central hub. Because the vanes are not coincident, it provides a bit of a challenge in terms of diffraction issues.




Not sure the fan thing is so complicated but good luck and I'm sure it'll work out fine for you...




On your 32" Webster, the spider vanes are perpendicular. Mine are only perpendicular to each pair neighboring each other. How do you remove your fan for collimation and what gauge/strand count wire did you use?




I also used the "Boundary Layer Fan" on my somewhat modified 22" Starmaster for several years (kinda wish I had that scope back...) with the same positive results. I always turned it off after a couple of hrs as its job was done.

Thanks for your updates on your new (and somewhat amazing) scope. Please continue to share how it works out for you.
Thanks, dave


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Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: nsldvd]
      #5548016 - 11/30/12 11:00 PM

Dave, As you can see by the thread that I will not only be utilizing the front boundary layer fan but will have a ducted rear sucking fan operating independently but also in concert with the front fan. What we found preliminarily is that if we only used the rear sucking fan, the image cleaned up almost immediately as you described but after several hours the primary mirror was showing overcorrection which Mike Lockwood attributed to the cooling of the outer circumference of the mirror but not having the center of the mirror cooling at the same rate. Hopefully, with experimentation, we will be able to determine just how much and how long the CBLMS (Comprehensive Boundary Layer Mitigation System) needs to be running and at what speeds are the fans optimal? I appreciate you sharing your empirical data as that will make the implementation of this system all that much smoother knowing what you have experienced in the past.

I talked with John Pratte the builder/designer at JP Astrocraft and he said that using the wire as an electrical conducter did not significantly impact the voltage going to the fan. As you know, we are exclusively using Maglev fans for both vibration reduction over conventional fans and longer fan life. Bob

Edited by Bob S. (11/30/12 11:03 PM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5548537 - 12/01/12 10:25 AM

Wow, simply . . . Wow.

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Peter Natscher
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5548760 - 12/01/12 12:58 PM

Hi Bob,

I wish you much observing enjoyment with your new 20" scope. John Pratte surely has done a beautiful job with your new scope. What are the CFM numbers and voltage draw of the MagLev fans on your cooling system -- back-side and front-side? Is the air gap between the primary's front-side baffle and mirror edge tight enough to create an effective venturi so that the front-side airflow against the primary will more effectively travel around the primary and onto the back-side fan for expulsion out the back? You don't want the air movement on the front-side of the primary to just boil and get trapped in a turbulent pattern. It needs to get away from the primary front surface in an orderly fashion for best effect. The moving cooler air needs to travel in a smooth way off of the primary and around the circumference and side of the primary expeditiously by the pull of the backside fan. I was almost there with this system cooling a 24" Starmaster but didn't get the front-side air flow right. None the less, the two backside fans and two side-mounted front-side fans (75 cfm each) had operating halved the cool-down time (vs. no fans) of the 24" f/3.6 primary with 0.75" thickness.

Quote:

Dave, As you can see by the thread that I will not only be utilizing the front boundary layer fan but will have a ducted rear sucking fan operating independently but also in concert with the front fan. What we found preliminarily is that if we only used the rear sucking fan, the image cleaned up almost immediately as you described but after several hours the primary mirror was showing overcorrection which Mike Lockwood attributed to the cooling of the outer circumference of the mirror but not having the center of the mirror cooling at the same rate. Hopefully, with experimentation, we will be able to determine just how much and how long the CBLMS (Comprehensive Boundary Layer Mitigation System) needs to be running and at what speeds are the fans optimal? I appreciate you sharing your empirical data as that will make the implementation of this system all that much smoother knowing what you have experienced in the past.

I talked with John Pratte the builder/designer at JP Astrocraft and he said that using the wire as an electrical conducter did not significantly impact the voltage going to the fan. As you know, we are exclusively using Maglev fans for both vibration reduction over conventional fans and longer fan life. Bob




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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5548853 - 12/01/12 02:01 PM

Bob,

How will the front-fan wiring affect your setup and breakdown assembly routines? Will it add time to an already simple observing routine? Of course, if you are only going to roll this baby out of your garage to observe and video, then it's a no brainer. Buy if this scope is one that will be transported, assembled, and disassembled at a remote site, how will you design the fan's wire suspension attachments to the trusses (or mirror box?) to retain easy setup, especially in the dark at 3am? The suspension wires must be easy attached and tight. I do all my observing at remote darker sites, and so I'm a *fan* of an uncomplicated telescope.

Quote:

Here is a picture of the forward fan in the up position so that I will be able to collimate the telescope. We are also considering the placement of the wires to add as little diffraction spike input as possible. You will notice that the ring is not round. It mimics the .42" offset of the secondary mirror.




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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Peter Natscher]
      #5548899 - 12/01/12 02:32 PM Attachment (67 downloads)

Quote:

Bob,

How will the front-fan wiring affect your setup and breakdown assembly routines? Will it add time to an already simple observing routine? Of course, if you are only going to roll this baby out of your garage to observe and video, then it's a no brainer. Buy if this scope is one that will be transported, assembled, and disassembled at a remote site, how will you design the fan's wire suspension attachments to the trusses (or mirror box?) to retain easy setup, especially in the dark at 3am? The suspension wires must be easy attached and tight. I do all my observing at remote darker sites, and so I'm a *fan* of an uncomplicated telescope.

Quote:

Here is a picture of the forward fan in the up position so that I will be able to collimate the telescope. We are also considering the placement of the wires to add as little diffraction spike input as possible. You will notice that the ring is not round. It mimics the .42" offset of the secondary mirror.







Peter, John has ingeniously designed the front mirror fan so that the suspension system is secured by 4 little turn paddles similar to Starmaster mirror clips and when rotated out of the way and when disconnected from the power source that is built into the top of the mirror box, the entire unit can be lifted out in seconds. I doubt that I will need to do that but it can be done. John has also crafted the mirror cover to sit above the fan unit and be locked in conveniently with the same type of "mirror clip" pieces but just higher so that it does not touch the fan system. I have included a picture of the lift off front fan assembly.

Edited by Bob S. (12/01/12 02:35 PM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5549855 - 12/02/12 06:49 AM Attachment (56 downloads)

Quote:

Quote:

Bob,

How will the front-fan wiring affect your setup and breakdown assembly routines? Will it add time to an already simple observing routine? Of course, if you are only going to roll this baby out of your garage to observe and video, then it's a no brainer. Buy if this scope is one that will be transported, assembled, and disassembled at a remote site, how will you design the fan's wire suspension attachments to the trusses (or mirror box?) to retain easy setup, especially in the dark at 3am? The suspension wires must be easy attached and tight. I do all my observing at remote darker sites, and so I'm a *fan* of an uncomplicated telescope.

Quote:

Here is a picture of the forward fan in the up position so that I will be able to collimate the telescope. We are also considering the placement of the wires to add as little diffraction spike input as possible. You will notice that the ring is not round. It mimics the .42" offset of the secondary mirror.







Peter, John has ingeniously designed the front mirror fan so that the suspension system is secured by 4 little turn paddles similar to Starmaster mirror clips and when rotated out of the way and when disconnected from the power source that is built into the top of the mirror box, the entire unit can be lifted out in seconds. I doubt that I will need to do that but it can be done. John has also crafted the mirror cover to sit above the fan unit and be locked in conveniently with the same type of "mirror clip" pieces but just higher so that it does not touch the fan system. I have included a picture of the lift off front fan assembly.




Peter, Something that I had not noticed myself until I studied the picture John sent me of the fan system was that he made accomodations for my concerns about adding diffraction spikes with the fan support wires because we are not using coplanar/collinear secondary spider vanes. If you look closely you will notice that the fan support wires utilize the same strategy that was used for rotational stability of the secondary mirror/holder on the wire support scheme of the frontal fan. The neighboring support wires are perpendicular to each other but not coincident but parallel to the support wire on the other side of the fan. When I saw John's drafting plans for the build of the UTA and his utilization of those plans for the frontal fan, I failed to initially realize that he has been able to maintain the same obstruction scheme thereby eliminating additional sources of diffraction spikes that had been a concern of mine.

Without sounding like an ad for John Pratte of JP Astrocraft which would be better served in the Vendor section, I am simply amazed at his forward thinking throughout the build process of this very custom scope. I was discussing studying Albert Highe's new book about the design and construction of Newtonian telescopes and Pratte had advised me that he had already gotten a copy and was reading many sections of the new book and was able to discuss specific chapters. Sheesh, I feel like one of the luckiest guys on the planet for having taken Mike Lockwood's suggestion to run the build requirements by John and see what he thought? Not to mention that a 20" f/3 1.25" thick Lockwood primary and 5" Lockwood secondary are not exactly chopped liver Bob


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5550263 - 12/02/12 12:30 PM

Quote:

Quote:

Very nice! What is that thingy abouve the focuser? It looks like another focuser.....



You can never have enough focusers Actually it is a 1.25"-2" holster for placement of my Mallincam when it is out of the focuser. The 1.25" portion of the holder is a Baader Clic-Lock device that requires just a slight turn of the knurled nob to secure the camera. You are also probably wondering about the turnbuckle on the front of the rockerbox/mirror box. That is used in conjunction with two sliding bolts on the rear of the mirror box that go into the rocker box to place it in an upright position to simply lean the telescope over and wheel it out to my observing site. The axles have quick release pins that allow the wheels to come off and the axle to be removed. However, you can observe with the wheels attached.



Bob,
What does the 1.25" Clic-Lock sit in and how did you mount it to the UTA, is a 2" focuser of some sort?
Thanks,
Frank


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: FrankG]
      #5550319 - 12/02/12 01:06 PM Attachment (72 downloads)

Quote:

Quote:

Quote:

Very nice! What is that thingy abouve the focuser? It looks like another focuser.....



You can never have enough focusers Actually it is a 1.25"-2" holster for placement of my Mallincam when it is out of the focuser. The 1.25" portion of the holder is a Baader Clic-Lock device that requires just a slight turn of the knurled nob to secure the camera. You are also probably wondering about the turnbuckle on the front of the rockerbox/mirror box. That is used in conjunction with two sliding bolts on the rear of the mirror box that go into the rocker box to place it in an upright position to simply lean the telescope over and wheel it out to my observing site. The axles have quick release pins that allow the wheels to come off and the axle to be removed. However, you can observe with the wheels attached.



Bob,
What does the 1.25" Clic-Lock sit in and how did you mount it to the UTA, is a 2" focuser of some sort?
Thanks,
Frank




Frank, That is a holster for my Mallincam astrovideo cameras when I have to take them out of the focuser. The picture below shows a Mallincam in the holster of the UTA.


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5550321 - 12/02/12 01:11 PM Attachment (95 downloads)

Astro Buds: One of the very cool features of the UTA and something that has caused many of us some pause is the flexing of the focuser board in the UTA. Pratte decided to reinforce the relatively thick focuser board with metal strapping that you will see below. He also used seperate struts for the spider vanes and seperate struts to keep the UTA rings stable. The spider vane struts also add increased stability of the UTA rings.

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FrankG
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5550336 - 12/02/12 01:20 PM

Quote:

Quote:

Quote:

Quote:

Very nice! What is that thingy abouve the focuser? It looks like another focuser.....



You can never have enough focusers Actually it is a 1.25"-2" holster for placement of my Mallincam when it is out of the focuser. The 1.25" portion of the holder is a Baader Clic-Lock device that requires just a slight turn of the knurled nob to secure the camera. You are also probably wondering about the turnbuckle on the front of the rockerbox/mirror box. That is used in conjunction with two sliding bolts on the rear of the mirror box that go into the rocker box to place it in an upright position to simply lean the telescope over and wheel it out to my observing site. The axles have quick release pins that allow the wheels to come off and the axle to be removed. However, you can observe with the wheels attached.



Bob,
What does the 1.25" Clic-Lock sit in and how did you mount it to the UTA, is a 2" focuser of some sort?
Thanks,
Frank




Frank, That is a holster for my Mallincam astrovideo cameras when I have to take them out of the focuser. The picture below shows a Mallincam in the holster of the UTA.



Right, I understand its a holster for the Mallincam -- what is the base -- the part the Cic-Lock sits in -- made from, a focuser, was it custom-built?
Thanks,
Frank


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: FrankG]
      #5550337 - 12/02/12 01:21 PM

The base was a part from the folks at Starlight Instruments.

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FrankG
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5550339 - 12/02/12 01:22 PM

Gracias

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5550371 - 12/02/12 01:46 PM

Quote:


Frank, That is a holster for my Mallincam astrovideo cameras when I have to take them out of the focuser. The picture below shows a Mallincam in the holster of the UTA.




That is one fancy-looking UTA! Looks like it could double as a control board for an Apollo landing craft


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: tezster]
      #5550410 - 12/02/12 02:09 PM Attachment (80 downloads)

Frank, Here are the holster components. It allows for either 1.25" or 2" items to be placed in the holster.

Edited by Bob S. (12/02/12 02:37 PM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: tezster]
      #5550420 - 12/02/12 02:12 PM Attachment (81 downloads)

Quote:

Quote:


Frank, That is a holster for my Mallincam astrovideo cameras when I have to take them out of the focuser. The picture below shows a Mallincam in the holster of the UTA.




That is one fancy-looking UTA! Looks like it could double as a control board for an Apollo landing craft




Terence, If you think that is wild, here is just a preview of the rocker box that incorporates machined corner braces and biscuit joinery along with a Gen III ServoCat install. You can barely see the stalk on the opposite side from the focuser that will hold my ultra book computer, wired and wireless remote controls, heater for the laptop screen, 12v converter to drive the ultrabook and God knows whatelse?

Edited by Bob S. (12/02/12 02:14 PM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5550441 - 12/02/12 02:23 PM Attachment (108 downloads)

Terence, I used to be a professional pilot many years ago so will strap in and take this baby for a ride (I actually had fantasies of installing an integral observing chair and having the scope counterbalanced so I could simply move with the telescope). Here is a better picture of the control stalk and then I will show one more with a mockup of the control panel. You will notice that all power to the scope comes in at one of two powered groundboard sockets that are on either side of the telescope. I chose two power inlet options because I primarily view things coming up from the East and wanted the input power cord on the opposite side from where I am sitting. If I want to spend most of my time viewing to the West, I can power the scope on the opposite side and thereby avoid any entanglement with the one and only power cord powering all of the doodads on the scope.

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5550445 - 12/02/12 02:25 PM Attachment (93 downloads)

This is a mockup of the control panel. I will have to create a checklist not unlike an aircraft to get my procedures down so that I can control the scope via the ultrabook's planetarium software that will interface with the ArgoNavis and also the Mallincam astrovideo camera. We have tried to think of everything and a friend mentioned that the glass screens were prone to dewing up. We will be building a metal hood surrounding the instrument panel that will be cork-lined and also have a heating element for the glass screen on the computer monitor so that it will not dew up. The hood will also screen any light from the telescope so that my astrovideo or visual activities will not be disturbed by ambient light. I can put a cloth shield over the hood opening to block any stray light from entering an observing site if I am at a dark site. The control panel was purposely placed on the opposite side from the focuser because this will be a total sit down scope and I did not want any podium/control panel to be anywhere near where I was sitting/observing. I will have the wireless remote control around my neck or somewhere so that I can manually move the scope with the controller without have to get off my chair.

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5550932 - 12/02/12 07:54 PM

What I like about this scope is that, despite all the 'stuff' attached, everything has its place and is neatly connected. I was about the ask about the wireless control, but you already mentioned the wireless control (although I was kind of thinking more about a wireless DSC connection i.e. to a tablet PC. I'm always a fan of seated observing (with feet on the ground), and this looks like the ultimate sit-down scope.

Something else I wanted to ask is, is a field-derotator needed with alt-az tracking, considering the short exposure times of a Mallincam?


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astrocrafter
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: tezster]
      #5550998 - 12/02/12 08:37 PM

The nice base for the holster is a 3.5" focuser end cap from Starlight. I removed 3 set screws in the base, drilled out the threads, and put a flat spotface on the holes as the base has a slight taper there, and presto! A slick looking 2" holster. Holds an extra eyepiece for visual observing too.
John


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: astrocrafter]
      #5551161 - 12/02/12 10:11 PM

Terence, The Mallincam exposures will generally be no more than about 30-45 second integrations. In that short of an accumulation time of the image, in most directions, the stars will not show much if any field rotation. I am glad that John, the scope designer/builder, jumped in on the fabrication of the 3.5" holster. About the only thing I can create is a wish list. He fortunately has the skills to operationalize the dreams<g>. Bob

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5551543 - 12/03/12 05:54 AM

Thanks, Bob!

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: FrankG]
      #5554958 - 12/05/12 01:05 AM

Impressive!! I can imagine the b/w classic film of Frankenstein and you wearing your white over-coat (smock)rubbing your hands together and as lighting strikes your lab above you, you chuckle in an evil way..."it's alive...IT'S ALIVE!!!" in the near future.

Nice story in the making. Impressive ingenuity in your build!


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: fnowat]
      #5556197 - 12/05/12 06:56 PM Attachment (81 downloads)

We are getting to the shorter strokes on this build. John Pratte just sent me a picture of the mirror box cover that will install with or without the front fan installed. You will notice two sets of tabs in the two corners of the mirror box. The lower set of tabs dimensionally holds the front fan frame down securely. The second set of tabs holds the mirror cover in place over the installed front fan. If I choose to not have the fan there, the cover is secured by what ordinarily will hold the fan frame. The reason for the trimmed corner edges on the mirror cover is that you have to do this to be able to get the cover out when you have the trusses installed. John advised me that we have gone to a heavier gauge wire and getting the tension correct is like collimating a piano, uh, I mean telescope<g>. In the upper right hand corner is the female RCA power outlet for the front fan that you simply plug into when utilizing the front fan. To say that I am getting excited would be a very gross understatement of how I am feeling

Edited by Bob S. (12/05/12 07:05 PM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5557898 - 12/06/12 05:10 PM Attachment (100 downloads)

As many of you know, when you are dealing with large/thin mirrors such as I am with the 20" f/3 being only 1.25" thick, you need a superlative mirror cell to prevent cell-induced abberations. Below is a picture of John Pratte with the mirror cell that he fabricated for the scope. The pads are riding on spherical bearings and the lower edge supports have rotating bearing surfaces to insure that there is no induced astigmatism from the cell. The cell was tested with the partially completed mirror at Lockwood's shop to check for any stig and there was no appreciable stig to be seen. You will also notice behind John is a 42" cell that is nearing completion. John can build them up to 60" (kind of makes my 20" look puny). For those of you contemplating custom scopes, I highly recommend that you insure that your mirror cell is up to the job that you are asking of it. Especially when the scope is approaching the horizontal position. Just about any mirror cell works when the scope is vertical. It is when there are tortional forces at play that the cell can either work for you or against you.

You can also see the rear sucking fan of the CBLMS (Comprehensive Boundary Layer Mitigation System) that has the Maglev fan suspended in sorbothane and sandwiched between support substructure that John used rivets to hold everything tight without inducing vibrations. BTW, the cell has built-in contact points that when installed in the scope transfer power from the ground board up to the rest of the scope. Bob


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5557917 - 12/06/12 05:19 PM Attachment (88 downloads)

Here is a close up pic of this beautiful mirror cell. As many will tell you, it is all in the details.

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5557952 - 12/06/12 05:33 PM Attachment (122 downloads)

This was a second-light picture of the scope back in the shop. The cast of characters from left to right is: John Pratte (Owner of JP Astrocraft), Bob Schilling (the bald/short scope developer), Bob From Illinois, Mike Lockwood (Owner of Lockwood Optics). You can see the early detail of the control table on the non-focuser side of the scope. This has a shield being built for it to house the ultrabook and keep it warm while preventing stray light. You can also see that beautiful 5" Lockwood secondary that as you know, is half of the optical train. My advice is, don't cheap out on the secondary

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tezster
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5558884 - 12/07/12 09:21 AM

Typically, large aperture reflectors tend to look bigger in photos where people are standing beside it and you're able to get a better sense of scale.

I think this is the first time I've seen a picture of a 20" where it actually appears SMALLER with people standing beside it. That is one short dob - I love short dobs


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: tezster]
      #5559430 - 12/07/12 02:43 PM

I'm really enjoying this build. It's pushing the state of the art and making future builds ever better. If I live long enough and keep my health, I'd sure like to get one like it. Ladders and darkness don't go well together.

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: audioaficionado]
      #5560192 - 12/07/12 11:55 PM

Hey, you listed John, Bob, Bob, and Mike...but who is the other un-named in the photo trying to get some attention?

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: fnowat]
      #5560290 - 12/08/12 01:26 AM

Quote:

Hey, you listed John, Bob, Bob, and Mike...but who is the other un-named in the photo trying to get some attention?



That would be Lucky, the attention-seeking dog.


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Mike Lockwood]
      #5560859 - 12/08/12 01:05 PM Attachment (93 downloads)

John P. completed the removable front fan with controller as part of the CBLMS (Comprehensive Boundary Layer Mitigation System). Doesn't the CBLMS just roll off your tongue<g>. Anyway, he went to a higher strength wire than originally spec'd and routed the power cables for the fan in the inside diameter of the ring and then out to the attach point on the top of the mirror box. The speed controller was placed in the corner where the power supply is. The fan is designed to be lifted up when collimating the scope and then resides in the shadow of the secondary during periods of operation. As mentioned earlier, the "strings" for the fan are coincident with the secondary spider vanes and will not add additional diffraction spikes.

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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5560866 - 12/08/12 01:08 PM Attachment (74 downloads)

The fan speed controller is conventiently located on the top of the mirror box for easy access. There is no doubt that the regulation of the front and back fans will require a learning curve to coordinate the scope needs with the varying temperature conditions that the scope will be operating in. This is a picture of the variable fan speed controller which is the same kind that is controlling the rear fan and that controller is accessible from the back of the mirror box. You can see the detail of the capture clips that are designed to hold the fan unit in place and the mirror cover above the fan when installed.

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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: tezster]
      #5562983 - 12/09/12 07:02 PM Attachment (90 downloads)

Quote:

Typically, large aperture reflectors tend to look bigger in photos where people are standing beside it and you're able to get a better sense of scale.

I think this is the first time I've seen a picture of a 20" where it actually appears SMALLER with people standing beside it. That is one short dob - I love short dobs




Terence, When John Pratte was in the early stages of testing the scope, he had it out and his wife took a picture of him next to the scope in the daylight. This will give you a better perspective of how a 20" f/3 can look with an ep height at zenith of 62". It will definetly be primarily a sit-down scope.

Edited by Bob S. (12/09/12 07:07 PM)


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5566230 - 12/11/12 04:23 PM Attachment (77 downloads)

Well, We continue to get closer and closer to completion. The control center cover has been constructed out of .040 aluminum and only weighs a couple of pounds. John temporarily used sheet metal screws to prove the final concept and after painting the shield inside/out it will be ready for final pop rivets. The inside of the control center shield will be lined with cork to prevent any sweating inside of the aluminum housing. John made the shield such that any water/dew accumulating on the outside of the shield will drip free of the internal components housed in the shield as well as the telescope innards.

Edited by Bob S. (12/11/12 06:58 PM)


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5575537 - 12/17/12 11:18 AM Attachment (82 downloads)

John Pratte at JP Astrocraft in Illinois and I gave birth to a strapping 20" f/3 baby boy this weekend. At least that is how it felt after the telescope completed its Autocal sequences of the ServoCat system. This is a shout out for the principal figures in the build in the following order: God, creator of everything; John Pratte, owner of JP Astrocraft; Mike Lockwood, owner of Lockwood Custom Optics, Gary Myers, owner of StellarCat/ServoCat; and my wife for putting up with my dreams (this one is out of the order). Here is a picture of the completed scope in the shop prior to taking it home.

Edited by Bob S. (12/17/12 01:35 PM)


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5575539 - 12/17/12 11:21 AM Attachment (72 downloads)

Here is a picture of the control panel/hood. The laptop has a warming pad from Kendrick that gently keeps the screen from dewing up. The control panel is cork-lined with a controller for the dew heater, wired and wireless handcontrollers and an Argo Navis tilted to get the best ergonomics. The orange dew heater actually is placed behind the laptop screen to keep it warm and not underneath the computer as is depicted.

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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5575543 - 12/17/12 11:24 AM Attachment (71 downloads)

Here is a picture of the successful computer control of the Mallincam Extreme through the telescope's internal wiring to the Mallincam.

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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5575546 - 12/17/12 11:26 AM Attachment (67 downloads)

Here is a another shop picture of the scope with me at the controls of this rocket ship.

Edited by Bob S. (12/17/12 11:26 AM)


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5575549 - 12/17/12 11:28 AM Attachment (85 downloads)

And lastly, this is an overall picture of the scope including the control center, etc. The only design features we did not incorporate were a weather station positioned on top of the hood and a piston-actuated servo-controlled viewing chair that would move in unison with the telescope's eyepiece position. Those features will have to wait for the next iteration from the JP Astrocraft/Schilling skunkworks

The telescope has three seperate wiring systems incorporated into the build that include: the ServoCat/Argo Navis/computer; the Mallicam control isolated to reduce/prevent radio frequency interference with/and from the dew control systems. The only batteries on the scope are in the Telrad. Everything else is powered by only one 12v power cable coming into one of the two powered-groundboard recepticles. No dangling wires to trip on and a very clean design.

Edited by Bob S. (12/17/12 03:02 PM)


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jwheel
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5575580 - 12/17/12 11:52 AM

Nice looking telescope Bob!

Joe Wheelock


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Mike Lockwood
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5575584 - 12/17/12 11:54 AM

Quote:

The only design features we did not incorporate were a weather station positioned on top of the hood and a piston-actuated servo-controlled viewing chair that would move in unison with the telescope's eyepiece position. Those features will have to wait for the next iteration from the JP Astrocraft/Schilling skunkworks



I hear those features will be incorporated into the 40" version.....


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tezster
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5575658 - 12/17/12 12:47 PM

Quote:

the Mallincam control isolated to reduce/prevent radio frequency interference.




Radio frequency interference from what? The telescope picking up extra-terrestrial broadcasts from deep space?


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Howie Glatter
Vendor


Reged: 07/04/06

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5575746 - 12/17/12 01:42 PM

"John Pratte at JP Astrocraft in Illinois and I gave birth to a strapping 20" f/3 baby boy this weekend."

How did you know it was a boy ? Ultrasound ?


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turtle86
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5576070 - 12/17/12 05:16 PM

Quote:

John Pratte at JP Astrocraft in Illinois and I gave birth to a strapping 20" f/3 baby boy this weekend. At least that is how it felt after the telescope completed its Autocal sequences of the ServoCat system. This is a shout out for the principal figures in the build in the following order: God, creator of everything; John Pratte, owner of JP Astrocraft; Mike Lockwood, owner of Lockwood Custom Optics, Gary Myers, owner of StellarCat/ServoCat; and my wife for putting up with my dreams (this one is out of the order). Here is a picture of the completed scope in the shop prior to taking it home.




That is one beautiful scope. You'll have to come up with a name for your "baby boy"!


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starman345
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: turtle86]
      #5576081 - 12/17/12 05:21 PM

Beautiful telescope Bob. Looks like you designed in the best of everything.

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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Howie Glatter]
      #5576410 - 12/17/12 08:56 PM

Quote:

"John Pratte at JP Astrocraft in Illinois and I gave birth to a strapping 20" f/3 baby boy this weekend."

How did you know it was a boy ? Ultrasound ?




Howie, Didn't you notice the long stalk? That's how we sexed it.


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johnnyha
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5576742 - 12/18/12 02:07 AM

Be-yooo-tee-full!

Is that going to have a SIPS installed Bob?


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: johnnyha]
      #5576791 - 12/18/12 03:42 AM

Quote:

Be-yooo-tee-full!

Is that going to have a SIPS installed Bob?




Johnny, A SIPS is indeed a part of the system. Do not know if it will work with the Mallincam and sure know it will not work with my binoviewers. I also have a HUGE 3" Starlight Instruments fine focusing knob for the SIPS that should make focusing a cinch with the native focal ratio of f/3 and it being more relaxed witht the SIPS. Bob


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5580160 - 12/20/12 07:30 AM Attachment (117 downloads)

Well Astro Buds, The 20" JPA finally got first light under Florida skies last night. The seeing was only about 6/10 and transparency was about 7/10 under an almost 1/2 moon. I was able to test the SIPS (Starlight Instrument Paracorr System) which worked wonderfully with my Ethos EP's presenting pinpoint stars to the edge on 17mm Ethos ep's. I think it was equally comfortable with the 21mm Ethos in terms of coma but did not spend enough time with the ep to determine how precise the starpoints were at the periphery. Jupiter was looking pretty decent with 8 and 10mm Ethos ep's.

After doing a non-critical two-star initial alignment, I did subsequent align on stars procedures with the Argo Navis and the scope with a 10mm Ethos was putting Jupiter and Uranus which were about 180 degrees apart right smack dab in the center of the eyepiece. I will include a couple of real-world pics since all of the others were in the shop.


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5580166 - 12/20/12 07:34 AM Attachment (111 downloads)

Here is a view on the focuser side of the scope. You will notice in the picure above that the whole scope is powered by one electrical cord. It turns out the that computer dew heater was pulling so much power that it caused my 5 amp regulated power supply to shut down due to overheating when I was running everything. I went to my 111 amp/hour marine battery and the scope ran like a charm. I left the front fan blowing on the face of the mirror on at the lowest setting after turing off the rear sucking fan. The mirror had equilibrated quite rapidly and there was no need for the rear fan.

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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5580168 - 12/20/12 07:37 AM Attachment (103 downloads)

It was a bit chilly last night and so I kept the wireless handpad in my coat pocket and directed the scope while pushing the buttons by feel. Gary Myers of ServoCat had made the handpad tactile friendly and it was easy to do. The integrated wheel system allowed for rapid deployment and return of the scope to the garage with a minimum of fuss and bother. Simply closed two latches on the back of the mirror box, tightened the turnbuckle on the front of the mirrorbox/rocker box, set the pin in the foot that correctly aligns the scope to the feet and tilted the scope over and rolled it in and out of the insulated garage. Could not be an easier way to begin viewing with a large scope. All systems so far are working well. Next step is to play with a Mallincam Hyper Plus directly connected to the 3.5" color LCD monitor positioned on the UTA and see how it works and if it will work with the SIPS in place? The rubber-backed carpet seems to prevent thermals from the driveway coming up much around the scope. However, I am eyeing that patch of grass in the picture as a likely more ideal setup spot to take advantage of the Northern sky and also to get off of the concrete. I have all my scopes able to roll rather than trying to carry anything which is a pain in the butt. The scope ergonomically is a dream. John Pratte tried to think of every way in which the scope would be user friendly and require the least amount of fiddling. We certainly accomplished all of the original design goals and a host of others almost too numerous to list. The 8 month collaborative effort produced some very interesting and unexpected features that neither of us would have dreamt of until we got into the build of the scope. I have had a tendency to buy and sell scopes over the years but this scope will be my permanent large aperture scope for now and into the future. As I age, utility and ease of use trumps many other potential options/benefits.

Edited by Bob S. (12/20/12 08:00 PM)


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Jarad
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5581419 - 12/20/12 08:36 PM

Congrats!

Maybe this will be the scope that finally permanently captures your heart.

And if not, I call first dibs!

Jarad


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Jarad]
      #5582675 - 12/21/12 03:22 PM

A significant proof of concept occurred today. I placed a glass of water on top of the front mirror fan frame that is mounted on Sorbothane mounting pads in the mirror box and turned the Maglev fan on at full to low speed settings and there was no vibration detected in the glass of standing water. I then turned on the much larger rear Maglev main sucking fan that is completely isolated in Sorbothane at full speed with the front fan going at full speed and rested it on the edge of the mirror box and there was no detectable vibration in the water. I then placed the glass of water with both fans going at full speed up on the ring of the UTA (upper tube assembly) to see if there was any harmonic vibrations being transmitted to the upper cage and there was no detectable vibration noted in the glass of water. This lack of vibration is likely attributable to the Maglev fans and mounting techniques. It is a very welcome finding suggesting that the relatively extreme measures that John Pratte of JP Astrocraft took to isolate the fans from causing vibration paid off handsomely.

Jarad, As the scope took shape and Mike Lockwood figured the primary mirror, at the completion of the mirror figuring, I had him inscribe my three initials with another set of three letters "RIP". My spouse will unfortunately have to have one of my buddies sell the scope when I die, become disabled or get out of the hobby

Edited by Bob S. (12/21/12 04:54 PM)


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5583741 - 12/22/12 09:06 AM Attachment (92 downloads)

A second significant proof of concept occurred earlier this morning of December 22. I equilibrated the scope from 5:20 until 6 a.m. using both front and rear fans of the CBLMS (Comprehensive Boundary Layer Mitigation System) and then proceeded to get first light of the year on Saturn which started at about 30 degrees above the horizon and by 7:30 a.m. was at about 60 degrees above the horizon. Saturn is a great target to test resolving capabilities and this morning's task was to ascertain how the fan systems would work with improving/degrading the image of the planet. I had my 10mm Ethos in the SIPS system which gave me 175x magnification. Seeing was about 6/10 and as the planet climbed higher in the sky continued to show more fine detail culminating in views with the Sun coming up but still presenting decent images until about 7:35 a.m.

In Illinois a month before the scope was completed, we only had the rear fan operational, on the first light night, we found that the image of Jupiter from an unequilibrated mirror cleaned up instantly when we turned on the enclosed sucking fan. We also found that using that fan at high speed by itself caused the primary mirror to shift into an overcorrected state per Mike Lockwood as he tested the mirror during the session. We all figured that adding the front fan would eleviate the overcorrection problem by not only cooling around the edges of the mirror but equally cool the center mass of the primary thus maintaining the neutral figure of revolution that Mike had put into the mirror.

This morning, my first task was to run the front fan only at the lowest speed which creates a gentle breeze on the front surface of the equilibrated 1.25" thick primary and the views of Saturn were good and getting better as it rose higher in the sky. I experimented with turning the front fan on and off and each time I turned it back on, the images were more detailed. So, that part of the CBLMS was proving itself to be additive.

Now, the big question in my mind and that of Lockwood and Pratte was if the rear sucking fan that is fully enclosed in the back of the mirrorbox coupled with the annulus that is in front of the primary mirror and about 1/2" larger in circumference than the front mirror would indeed draw air off the boundary layer and thus contribute to an improved image? I am VERY happy to report that it indeed worked. The most detail seen in the Cassini Division and other parts of the ring structure including the surface detail of Saturn were when the entire CBLMS consisting of the front blowing fan and the rear sucking fan were operating at their lowest rpm settings. Below is a picture of the scope pointing at Saturn this morning at 7:30 a.m.


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5583758 - 12/22/12 09:20 AM Attachment (107 downloads)

Now, there is another side-story that continues to evolve and is making this for me, the finest visual scope that I have ever used. As many of you know, I elected to incorporate the Starlight Instrument Integrated Paracorr System as the f/3 seemed to dictate the need for this as well as to not have to fiddle with Paracorr II settings in the conventional Paracorr. With the SIPS system, any eyepiece used is corrected best for coma by the system. The second neatest feature of this system is the large 3" brass focuser knob that Starlight Instruments sells for their SIPS system that made focusing the most pleasant experience that I have EVER had! I cannot even begin to figure what the ratio is but with gloved hands this morning, just a light touch of the knob and the focus was at the pinnacle of perfection. As many of you know who own fast systems, focusing with a very limited depth of field can be a little bit of a challenge. Couple that to the changing seeing conditions and fiddling with the focuser knob even in a conventional Feathertouch focuser is a bit demanding. With the large 3" knob, all of these challenges fall to the wayside. It is so simple to lightly touch the wheel to get best focus that I was almost hoping for seeing changes just to play with the large knob. It is sooooooooo easy. Here is a picture of the 10mm Ethos in the SIPS with a dew strap on the ep and the 3" focuser knob that operates the fine-focus of the Feathertouch.

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Bill Barlow
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5583868 - 12/22/12 11:03 AM

I'm envious, Bob. Would love to get a few looks through the eyepiece of this fine instrument. Enjoy!

Bill


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Relativist
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5584328 - 12/22/12 04:22 PM

Quote:

A significant proof of concept occurred today. I placed a glass of water on top of the front mirror fan frame that is mounted on Sorbothane mounting pads in the mirror box and turned the Maglev fan on at full to low speed settings and there was no vibration detected in the glass of standing water. I then turned on the much larger rear Maglev main sucking fan that is completely isolated in Sorbothane at full speed with the front fan going at full speed and rested it on the edge of the mirror box and there was no detectable vibration in the water. I then placed the glass of water with both fans going at full speed up on the ring of the UTA (upper tube assembly) to see if there was any harmonic vibrations being transmitted to the upper cage and there was no detectable vibration noted in the glass of water. This lack of vibration is likely attributable to the Maglev fans and mounting techniques. It is a very welcome finding suggesting that the relatively extreme measures that John Pratte of JP Astrocraft took to isolate the fans from causing vibration paid off handsomely.

Jarad, As the scope took shape and Mike Lockwood figured the primary mirror, at the completion of the mirror figuring, I had him inscribe my three initials with another set of three letters "RIP". My spouse will unfortunately have to have one of my buddies sell the scope when I die, become disabled or get out of the hobby




Very nice. If you have an iPhone you could use iSeismometer (or similar app) as well. The best measurement would be to use a laser, that said if you don't notice any difference visually then I wouldn't worry about it further.


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nsldvd
sage


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5584498 - 12/22/12 06:42 PM Attachment (66 downloads)

Quote:

The second neatest feature of this system is the large 3" brass focuser knob that Starlight Instruments sells for their SIPS system that made focusing the most pleasant experience that I have EVER had!




That's a great addition to the SIPS. A while back we could see the light bulb turning on when John Joseph was at Chiefland. It's really just a big plus for any focuser w/or w/out SIPS, fast or slow...


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johnnyha
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5585020 - 12/23/12 01:55 AM

Bob that's the first I've seen the Jumbo Knob. I'd really like to know how much more it sticks out than the original little fine focus knob but I can't find the dimensions - can you estimate approximately how much?

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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: johnnyha]
      #5585360 - 12/23/12 10:46 AM

Quote:

Bob that's the first I've seen the Jumbo Knob. I'd really like to know how much more it sticks out than the original little fine focus knob but I can't find the dimensions - can you estimate approximately how much?




Johnny, The original gold fine focuser knob's diameter is 13/16". The new focuser knob which is $49 from Starlight Instruments is 3" in diameter. They list a 1.75" brass knob for $29. The 3" knob is pretty intrusive and frankly can only be used when the SIPS is in place. I would suspect that the 1.75" knob might have more clearance for some applications? I am thinking that I would like to try the 1.75" knob and see how that feels. Bob


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johnnyha
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5585782 - 12/23/12 03:11 PM

Bob thanks. What I was wondering though, is what is the total thickness rather than the diameter? In other words how far extra does the jumbo knob protrude outwards? The jumbo knob looks to stick out at last 1" whereas the original fine focus knob is about 1/2".

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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: johnnyha]
      #5586036 - 12/23/12 05:55 PM

Quote:

Bob thanks. What I was wondering though, is what is the total thickness rather than the diameter? In other words how far extra does the jumbo knob protrude outwards? The jumbo knob looks to stick out at last 1" whereas the original fine focus knob is about 1/2".




Johnny, The 3" large fine-focus knob protrudes out from the attachment point 1 3/8" as opposed to the 1/2" of the stock fine-focus knob. Bob


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johnnyha
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5586382 - 12/23/12 10:26 PM

Bob thanks, so it sticks out an extra 7/8", thats about what I thought. Anyway... that is one masterpiece of a scope you have put together, truly. Kudos.

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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: johnnyha]
      #5586617 - 12/24/12 03:07 AM

Quote:

Bob thanks, so it sticks out an extra 7/8", thats about what I thought. Anyway... that is one masterpiece of a scope you have put together, truly. Kudos.




Johnny, It has been a lot of fun developing this scope with the help of John Pratte, Mike Lockwood and Gary Myers. I had an interesting conversation with Fast Mike who owns a 28" f/2.75 Lockwood/Webster this afternoon and we were comparing notes on SIPS system performance, eyepiece performance in ultra-fast scopes, cooling fan strategies and secondary mirror holder arrangements. As you may remember, Fast Mike's scope is sporting a 7" diagonal whereas mine is only 5" in the minor axis.

One of the things that we both have found is that the 17mm TeleVue Ethos is very close to bottoming out for in-travel when using the SIPS and gives about 1/2 turn of the fine focuser knob "freeboard" from the bottom of the 1.5" focuser travel to come to focus. He mentioned this is true of the 31mm Nagler which I have not tried using yet in my scope.

An interesting but slightly disconcerting thing we both encountered was that the Leica ASPH Vario zoom with 2" adapter is needing about 1/8" of further in-travel to come to focus with an unmodified adapter from APM. If you shave off the 1/4" ridge on the top of the adapter, the ASPH will come to focus with no problems. Not a big deal but there are always some new things that you discover on the way to the observing field

What was very interesting is that his eyes (Fast Mike) and my eyes found the SIPS position to be relatively similar and I had independently confirmed the amount of "freeboard" with the 17mm Ethos and the SIPS. He pointed out that because the in-travel requirements were the most extreme for the 17mm Ethos and the 31mm Nagler, he uses the 17mm Ethos as the reference for getting proper positioning and sharpest focus of the SIPS rather than the Scotch tape method recommended by the manufacturer and the plastic device they supply. What we both noticed is that that particular method utilizes tape that can vary and requires glasses or a magnifying glass to check best correction when applied and thus potentially throws off the proper tuned position of the SIPS system. Fast Mike has found that the use of the 17mm Ethos is a more reliable method for setting the SIPS and I plan to use the same method.

What the above-mentioned circumstances remind me of is that when you get into faster and faster equipment that is pushing the envelope, there are things to be discovered and accomodated for. Mel Bartels was giving a lecture on the design of Newtonians that I attended out at the Golden State Star Party this past year in California and he noted that the equipment like eyepieces and coma correctors were the limitations imposed for fast optics and that the demand, and manufacturer's response to the demand, helps set the bar as to what our limits will be. I know that there are numerous people that are contemplating scopes in the 40"-70" range that will want their optics to be in the sub f/3 range and as Bartel's pointed out, the only limits are what the optics manufacturers are willing to supply us with. The TeleVue and Starlight Instruments companies among others are helping us to explore ever faster optics that will perform at the levels that some of us demand in our premium Newts. It is a very fun time to be in the hobby and it is a blessing that we have very talented folks that can help us operationalize our dreams. Bob

Edited by Bob S. (12/24/12 03:46 AM)


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cpr1
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5586959 - 12/24/12 10:36 AM

Amazing scope Bob. It reminds me of the atomic bomb "fat man" for so reason.

Just curious as to why the argo navis/computer is on the opposite side of the focuser?


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: cpr1]
      #5587013 - 12/24/12 11:10 AM

Christopher, I would hope that the scope would remind you of things much grander and more pleasant than an A-bomb. I was born in Tokyo 4 years after the end of WWII and that was a sad era for the world and a very sad era for our Japanese friends.

On a brighter note, the reason for placing the command center on the other side of the scope is that I wanted to be able to comfortably sit at the eyepiece without the glare of computers/video output being anywhere near the eyepiece area or bouncing off the light path when doing astrovideo. I also wanted an unobstructed sitting area at the eyepiece for the 50% of the time that I will be using the scope visually. The other 50% of the time, the command center houses a laptop computer with planetarium program that will inform the ArgoNavis and also control my Mallincam Extreme astrovideo camera. The control center also houses the wired handpad and allows me to carry the wireless handpad with me wherever I am around the scope. It has a power transformer for the laptop's precise power needs and with all of those wires, it made sense to me to place the command center on the opposite side of the scope. As you can see, the control center is rather large and I did not want it to interfere with the operation of the scope.

Edited by Bob S. (12/24/12 11:11 AM)


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Project Galileo
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5587019 - 12/24/12 11:12 AM

Bob, congratulations on your wonderful telescope. It has been a joy watching this thread. It truly is an amazing instrument you gentlemen have created. I applaud you all for breaking thru the previous limits. Inspirational. Magnificent. Beautiful.

Your telescope's CBLMS (Comprehensive Boundary Layer Mitigation System) has been of special interest to me. My experience with sealing up the rear of my mass produced LB16, adding a baffle, and installing a sucking fan has had me watching with interest how your system works. I am pleased to hear your favorable findings of this system. Although I do not have the front mirror and only employ a portion of the CBLMS with the sucking fan, I have also reported similar improvements with it's use. Like you have stated earlier in this thread I have also found that images from an unequilibrated mirror clean up instantly when I turn on the sucking fan.

I hope that future telescope designers employ many of these breakthrough and functional improvements to the large, fast Dobsonians of the future. Cutting edge Indy Car or NASCAR design and innovations make it into our production cars. I like to think you guys are the cutting edge Indy Car or NASCAR guys of our hobby and I look forward to many of these innovations and design improvements making it into the production telescopes of the future as well.


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cpr1
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5587346 - 12/24/12 02:45 PM

Not to get in a debate about if it was right or wrong. But sorry that bothered you. Nice scope anyway. Thanks for the reply.

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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: cpr1]
      #5587394 - 12/24/12 03:21 PM

Quote:

Not to get in a debate about if it was right or wrong. But sorry that bothered you. Nice scope anyway. Thanks for the reply.




Christopher,

No offense taken and it does look pretty squatty Thank you for appreciating the scope and Merry Christmas!

Doc, Thank you for your kind words about the scope. We tried to incorporate just about every positive feature that we could think about. The development has been a lot of fun and taking risks is part of the game. We follow in the footsteps of others that have taken risks and the only way to advance the hobby as you know is to take some risks. So far, the rewards have been plenty. I have much more testing/experimentation left to do before I declare it a full/partial success. I have the ability to move the UTA into one of three positions with three different sets of UTA attach pieces of hardware which will allow for a full range of use with different equipment (I hope).

Bob

Edited by Bob S. (12/24/12 07:36 PM)


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5588449 - 12/25/12 12:56 PM Attachment (90 downloads)

As part of the build, I asked John Pratte to include some counterweights just in case I used something ultra heavy with the UTA/focuser. He came up with a very novel solution that not only fits perfectly onto the crossbars of the mirror frame but is elegantly simple (not everything on the scope is high-tech). It involves rare earth magnets that were intended for other applications. He removed the hook from the two sizes of magnets, ground the metal housings surrounding the magnets so they were smooth and then installed them in shrink wrap tubing that he shrunk around the magnets. The shrink wrap reduced the strength of the magnets just the right amount so they will not ever inadvertently come off but are able to be removed without using a crowbar The nice thing is that you can place them anywhere on the mirror cell frame to get just the right amount of counterbalance needed. The scope turned out to be almost perfectly balanced for most general applications from the light 10 ounce Mallincam up to my 31 Nagler and a 2x Powermate. When we were putting them together, it was like making magnetic sausages.

Edited by Bob S. (12/25/12 05:47 PM)


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5591554 - 12/27/12 06:05 PM Attachment (78 downloads)

People have been asking about the front fan arrangement on the CBLMS (Comprehensive Boundary Layer Mitigation System). I am including a more closeup picture and will provide dimensions that folks were asking about. The fan itself is about 9 inches above the primary suspended with .010 gauge wire. The annulus in the picture is about 1 inch above the primary and is about 1/2 inch wider than the mirror to allow for the venturi effect of the rear sucking fan of the CBLMS. You will notice that the front fan ring is held down by two keepers that swing out over the sorbothane pads on the top of the fan ring. The keeper not in use in the picture is used to keep the mirror cover on securely on top of the fan unit. If I remove the fan unit, the mirror covers has provisions to secure the mirror from the elements and the keepers were designed to work with that scenario as well. The fan ring itself has 4 pads underneath that also are there to mitigate any possible vibration. This is in addition to the fact that the blowing fan is a Sunon MagLev fan that is a very low vibration brushless motor fan with a long service life. As I mentioned earlier, the fan, set at the lowest speed seems to increase the performance of the primary in terms of gently blowing away some of the boundary layer. At high speed, it is used to equally cool the primary during initial cooldown.

Edited by Bob S. (12/27/12 07:10 PM)


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astrocrafter
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5591740 - 12/27/12 08:11 PM

Actually the wires are .025" dia. stainless. We first tried .015" but were afraid it was just too fragile. We are using safety wire which is not real strong, but forms loops nicely. A harder wire in a thinner gage might be better.
John


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: astrocrafter]
      #5591833 - 12/27/12 09:09 PM

Thanks for the correction above on the wire gauge John. Well, more testing with the fans on vs. off. The fans win! Both running simultaneously presented the steadiest images of Jupiter tonight with rather poor seeing. The GOTO's with the ServoCat/ArgoNavis were hitting all kinds of objects at 170x with a 10mm Ethos in the focuser.

I tried using a Paracorr II instead of the SIPS and my 21mm Ethos would not come to focus for lack of infocus ability. With the Sips, it required about 1/4" of out focus. This tells me that the SIPS fundamentally is doing something different with the light and that the Paracorr II is doing something different than the SIPS. Don't know what is up with that?

I can say that I do not really miss the Paracorr II much. It is so nice to just place an eyepiece in the focuser and it have pinpoint stars without messing with a Paracorr setting.

The seeing has been so poor since I brought the scope home that I have not had a chance to do any high-powered testing. That will come when all of these storms that have been ravaging the East Coast go away.

Hope everyone had a great Christmas and wishing everyone a very Happy New Year! Bob


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astrocrafter
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5592572 - 12/28/12 12:02 PM

Well we figured out what was going on with the 21 mm Ethos/ParacorrII not focusing. Bob had left the SIPS housing in place under the focuser, but removed the lens. The housing adds about 2" to the focuser height so he lost that much in-focus. Obviously he needs more training in telescope operation.
John


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Mike Lockwood
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: astrocrafter]
      #5592610 - 12/28/12 12:34 PM

Quote:

Well we figured out what was going on with the 21 mm Ethos/ParacorrII not focusing. Bob had left the SIPS housing in place under the focuser, but removed the lens. The housing adds about 2" to the focuser height so he lost that much in-focus. Obviously he needs more training in telescope operation. John




...and so ends another episode of "The Sleep Deprived Astronomer".

Tune in next week when Bob dozes off while Mallincamming and dreams he's imaging Halley's Comet.... at 25th magnitude.


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jim molinari
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Mike Lockwood]
      #5592727 - 12/28/12 01:50 PM

Bob ...
Thanks for sharing all the information on the design and use of this beautiful and innovative telescope. It has been a interesting, informative, and pleasurable to follow. Keep on enjoying ... you can sleep later!

Jim


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SkyRanger
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: jim molinari]
      #5592951 - 12/28/12 04:39 PM

Great scope, Bob.

BUT it just makes me want to order one of JPs Sweet Sixteens!

Gordon G


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: SkyRanger]
      #5597476 - 12/31/12 07:30 AM

Gordon, John's Sweet Sixteens are a very nice balance of practicality and largish aperture.

It is funny but a buddy of mine who is a hardcore user of large telescopes without fans really challenged my findings and was asking very detailed questions about the methodology used in my recent experiments. I very much welcomed the challenge because in many ways, this scope was developed to see if we could break some of the myths that exist with larger/fast mirrors. I have not had extensive enough time to test the various subsystems we built into the 20" f/3 JPA but there is plenty of time in 2013 to ascertain what has worked and what does not work.

My friend's greatest incredulity was that the CBLMS could be effective even when the thin 1.25" 20" mirror was seemingly fully equilibrated. It may just be that equilibration of the mirror to the ambient temperature that it is operating in is not the only criteria needing to be met for the most optimal views? This possible myth will be tested out many times in the coming year to ascertain what seems to improve/degrade our views. 2013 should be a very exciting time and I am looking forward to seeing what this very fun scope is capable of doing. Happy New Year to one and all. Bob Schilling


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johnnyha
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5599816 - 01/01/13 03:21 PM Attachment (57 downloads)

Bob I wanted to thank you for posting that photo of the SIPS with the new giant brass fine-focusing knob! My 15" Obsession has a low profile Feathertouch so I ordered the large 1.75" knob - beautiful! These larger fine focus knobs should be a great option for anyone with a fast scope.

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BrendanF
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: johnnyha]
      #5603502 - 01/03/13 06:44 PM

Great customized scope! It looks like you have to be careful of getting bashed by the control box when doing large azimuth slews.

I could not get my Mallincam to focus with my SIPS installed on my 20" f/3.3 (when I tried one time). I does great without the SIPS, though, so I don't worry much. I like to run my Mallincam with my MFR-3 (with and without a 5mm extension) to get to ~f/2. When observing at f/2, it becomes very obvious when anything goes out of alignment.

The only issue is removing the SIPS focuser bit--the tiny set screws on the focuser base are a pain. It takes more time than it seems like it should.

I just acquired an Ethos 17 (during the sale). Could you detail a bit more how you use it to set the SIPS position? Do you just rack the 17 all the way in and then move the SIPS to get the best focus?


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: BrendanF]
      #5603544 - 01/03/13 07:10 PM

Quote:

Great customized scope! It looks like you have to be careful of getting bashed by the control box when doing large azimuth slews.

I could not get my Mallincam to focus with my SIPS installed on my 20" f/3.3 (when I tried one time). I does great without the SIPS, though, so I don't worry much. I like to run my Mallincam with my MFR-3 (with and without a 5mm extension) to get to ~f/2. When observing at f/2, it becomes very obvious when anything goes out of alignment.

The only issue is removing the SIPS focuser bit--the tiny set screws on the focuser base are a pain. It takes more time than it seems like it should.

I just acquired an Ethos 17 (during the sale). Could you detail a bit more how you use it to set the SIPS position? Do you just rack the 17 all the way in and then move the SIPS to get the best focus?




Brendan, You need to really first follow the procedures for setting the SIPS with the scotch tape and the plastic insert. After you have done that, you can use the 17mm Ethos as a reference point for where best focus is from the bottom of the focuser travel outward. Fast Mike and I found that about 1/2 turn of the fine focus knob out from the bottom was where the 17mm Ethos was at best focus for the SIPS. You can use whatever the distance is with the Ethos rather than the tape to ascertain best focus using the eyepiece and a target rather than the tape method which is a bit sketchy.

Bob


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BrendanF
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5603588 - 01/03/13 07:42 PM

Bob,

I have set my SIPS using the tape and plastic pipe bit per the instructions from SI. I am just unclear on how you and Fast Mike were using the Ethos 17 to tweak the SIPS position in a 'less sketchy' method than the tape.

Maybe I just need to get out and experiment a bit now that I have an E17. I can always go back to the tape method if I tweak it in a bad way.

Cheers,

Brendan


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: BrendanF]
      #5603610 - 01/03/13 07:52 PM

Quote:

Bob,

I have set my SIPS using the tape and plastic pipe bit per the instructions from SI. I am just unclear on how you and Fast Mike were using the Ethos 17 to tweak the SIPS position in a 'less sketchy' method than the tape.

Maybe I just need to get out and experiment a bit now that I have an E17. I can always go back to the tape method if I tweak it in a bad way.

Cheers,

Brendan




Brendan, For Fast Mike and I, we put in the 17mm Ethos, back it out 1/2 turn of the fine focus knob, lock the focuser and then tune the SIPS to get the sharpest image in the 17mm Ethos. Fast Mike and I happen to have the same focus position but each persons eyes are different so you have to first use the proper SIPS method and then see how far off the bottom of focus the 17mm Ethos has to come to be at sharp focus. Using the Ethos instead of the tape allows for a clearer observation of best focus position for the SIPS as opposed to looking at an object on cellophane tape. Bob

Edited by Bob S. (01/03/13 09:29 PM)


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Mike Lockwood
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5603761 - 01/03/13 09:54 PM

Quote:

You can use whatever the distance is with the Ethos rather than the tape to ascertain best focus using the eyepiece and a target rather than the tape method which is a bit sketchy.



Sketchy is not the word I'd use.

Both methods work and are basically equivalent.

The tape method (which TeleVue described to me so that I could write the SIPS manual) directly locates the focal plane, which lies where the sharpest image forms on the tape.

The eyepiece method locates the focal plane by using the eyepiece to image it (that's whan an eyepiece does), making it easier for those who simply can't focus their eyes as well on the tape.

Alternatively someone could use a magnifier or low-power microscope to more closely examine the image formed on the tape.

Very interesting to have this thread and the mirror cooling thread going at the same time. This 20" is one of the few scopes that I've seen that can do what I always recommend - cooling the mirror evenly on all sides. Of course it can also do more than that!


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turtle86
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: johnnyha]
      #5604286 - 01/04/13 08:57 AM

Quote:

Bob I wanted to thank you for posting that photo of the SIPS with the new giant brass fine-focusing knob! My 15" Obsession has a low profile Feathertouch so I ordered the large 1.75" knob - beautiful! These larger fine focus knobs should be a great option for anyone with a fast scope.




Johnny, that 1.75" knob looks great and I really think it will help with the fine focusing. I have a low-profile Feathertouch myself so I just ordered the 1.75" for my Starmaster.


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johnnyha
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: turtle86]
      #5604601 - 01/04/13 11:32 AM

Thanks Rob, I haven't had a chance to use it yet but it's pretty obvious, this should give me about 6X more fine focus over the little 10:1 stock knob, which on such a fast scope is really appreciated. This should be a no-brainer for anyone at f4 and below.

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astrocrafter
Vendor (JP Astrocraft)


Reged: 11/24/10

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: johnnyha]
      #5604823 - 01/04/13 01:37 PM

I usually use my 6" scale as a knife edge on the plastic pipe to determine the focal plane when installing the SIPS.
John


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turtle86
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: johnnyha]
      #5605163 - 01/04/13 04:35 PM

Quote:

Thanks Rob, I haven't had a chance to use it yet but it's pretty obvious, this should give me about 6X more fine focus over the little 10:1 stock knob, which on such a fast scope is really appreciated. This should be a no-brainer for anyone at f4 and below.




Totally agree. My old SCT had a large focuser knob that I found helpful even though it was a slowish f/10. My present Starmaster is f/4.3 so I figure a larger knob will be all the more useful, especially when others view through the scope and on cold nights when I'm wearing gloves. I'm sure that the 1.75" knob will suit me fine, but wish I had room for that jumbo 3" one. What a conversation starter...


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: turtle86]
      #5605386 - 01/04/13 07:01 PM

You know you have been bit by the bug in more ways than one when after 5 days of trying to get over the flu, you are out testing an eyepiece Well, it was only for 5 minutes but I HAD to do it because my Leica ASPH Vario Zoom had not been coming to focus with the use of the SIPS. I was lacking just a fraction of an inch of in-travel but that is about as good as a mile when it comes to the SIPS because moving the mirror up just causes you to have to move the SIPS relationship.

Fast Mike was kind enough to clue me to this with his 28" f/2.75 Lockwood/Webster which was also not allowing the ASPH to come to focus. Well, John Pratte being such a nice guy, asked me to send him the two-inch adapters I have for the ASPH's and he machined a ridge off of the top part of the adapter that allowed the Leica ASPH to go into the SIPS equipped Feathertouch 9mm deeper. This silly little 9mm's allows me to now be able to have the Leica racked out a full half-turn of the gross focuser knob which gives me lots a leeway to get the eyepiece to come to focus. As some of you know who have been following the eyepiece forum here on CN, the Leica is one very high-performing zoom that allows widefield views with the performance that matches and can even exceed a Zeiss Abbe Ortho II under some circumstances. Unfortunately/fortunately, I am too sick and the skies are too *BLEEP* to risk a hospitalization. I can't wait to see how the ASPH performs in this new scope. Will be reporting on that in the coming weeks if the skies clear up here in North Florida. Bob

Edited by Bob S. (01/04/13 07:55 PM)


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a__l
professor emeritus


Reged: 11/24/07

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5605742 - 01/04/13 11:08 PM

Quote:


Brendan, For Fast Mike and I, we put in the 17mm Ethos, back it out 1/2 turn of the fine focus knob, lock the focuser and then tune the SIPS to get the sharpest image in the 17mm Ethos. Fast Mike and I happen to have the same focus position but each persons eyes are different so you have to first use the proper SIPS method and then see how far off the bottom of focus the 17mm Ethos has to come to be at sharp focus. Using the Ethos instead of the tape allows for a clearer observation of best focus position for the SIPS as opposed to looking at an object on cellophane tape. Bob




Bob, you get to combine the SIPS and MallinCam? What do you use 2" Focuser Dob Adapter is back or MFR-3 Focal Reducer or no?
You reduce the length of the tubes or use a different method, or no?


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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: a__l]
      #5606155 - 01/05/13 09:08 AM

Quote:

Quote:


Brendan, For Fast Mike and I, we put in the 17mm Ethos, back it out 1/2 turn of the fine focus knob, lock the focuser and then tune the SIPS to get the sharpest image in the 17mm Ethos. Fast Mike and I happen to have the same focus position but each persons eyes are different so you have to first use the proper SIPS method and then see how far off the bottom of focus the 17mm Ethos has to come to be at sharp focus. Using the Ethos instead of the tape allows for a clearer observation of best focus position for the SIPS as opposed to looking at an object on cellophane tape. Bob




Bob, you get to combine the SIPS and MallinCam? What do you use 2" Focuser Dob Adapter is back or MFR-3 Focal Reducer or no?
You reduce the length of the tubes or use a different method, or no?




A___I, I have not had a chance to experiment with a Mallincam in the telescope at this point. My first and only attempt, I had taken out the SIPS glass but had not returned the focuser to the non-SIPS position which is about 2" closer to the primary. It was an operator error that I will hopefully not repeat. The weather has been poor for astronomy in North Florida and my wife and I both have been dealing with a really nasty case of the flu which we seem to be finally improving from after being symptomatic for 5-6 days. Bob


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5607682 - 01/06/13 01:44 AM

Bob, but for what you have cleaned the glass SIPS? F/3.0 coma and big enough for Mallincam (probably?). Incompatibility SIPS and Mallincam?
I would be very interested to read the result of using SIPS (complete) + Mallincam + yes/no FR ...


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: a__l]
      #5608546 - 01/06/13 02:38 PM

I'm also anxious to hear the answers on the SIPS + Mallincam and how you achieve final focus.

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Busguy]
      #5610773 - 01/07/13 07:25 PM

I asked an additional question in the subject Video and Electronically Assisted Astronomy:

I want to determine the position of the focus for Mallincam.
The focuser on my Dob set to eyepieces Ethos-17,21 and Nagler-31.
Here
http://www.televue.com/engine/TV3b_page.asp?id=214

Eyepiece Specifications for TV eyepieces.
Table Notes F - Approx. location of field stop (negative number is above reference surface).
For E-21, 17 and N-31, respectively -0.38, -0.39 and -0.38.
This is the minimum benchmark. Below focuser travel impossible.
If you remove the Mallincam (focus OK) and set TV eyepiece. Which TV eyepiece is in focus (does not need to turn the knob focuser)? Or near the to the focus?
If you are using a 1.25/2" adapter for Mallincam or desired TV eyepiece I also need an height adapter on above surface focuser.
If the TV eyepiece is 1.25/2" skirt, it is correct to use a 2" eyepiece position.
Thanks.


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: a__l]
      #5614610 - 01/09/13 10:25 PM

A___I and Busguy, I was finally able to plug in my Mallincam Xtreme with the 1.25" nosepiece and a 10mm spacer with my SIPS in place and the camera came to focus on M42. I only had about 1/4" of out-travel available but it worked! I was frankly a bit astonished.

Tonight, even though the weather has been terrible in North Florida and was pretty lousy all day, the seeing was very steady at times and I was able to use 373x and 474x on Jupiter with the CBLMS (Comprehensive Boundary Layer Mitigation System) running. The best views were at 373x with my 4.7mm Ethos. The GRS and following white ovals were prominent at times. The long blue festoons in the NEB were also pretty apparent and I am scheduled to get cataract surgery which will greatly increase my blue sensitivity. I was suppose to have the right eye done today but am getting over the flu and was in no condition to get eye surgery. Wasn't even in good enough shape to work more than about 2 hours today but when it came to astronomy, I was so photon starved that I was out for more than 2 hours tonight. I guess my priorities are still good Bob

Edited by Bob S. (01/10/13 06:11 AM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5616752 - 01/11/13 07:13 AM

Quote:

A___I and Busguy, I was finally able to plug in my Mallincam Xtreme with the 1.25" nosepiece and a 10mm spacer with my SIPS in place and the camera came to focus on M42. I only had about 1/4" of out-travel available but it worked! I was frankly a bit astonished.





Bob, I'm glad that it worked!
I do not understand the nuances.
1. SIPS was set with a view to focus Ethos 17 and focuser with a maximum travel inside?
2. You have used 1.25/2" adapter (with Mallincam)? What is the height this adapter above plane focuser?
3. What is a 10mm spacer? Where it is set?
4. Height focus Mallincam 1/4" (travel focuser 1/4" outside of focus from the ethos 17)?
If you can, please place the a picture with dimensions.
Thanks.


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: a__l]
      #5617542 - 01/11/13 04:19 PM

Bob, sorry if I missed it but can you give an assessment of the Leica zoom on and off axis at f/3+paracorr? Thanks.

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Sgt]
      #5617557 - 01/11/13 04:28 PM

Quote:

Bob, sorry if I missed it but can you give an assessment of the Leica zoom on and off axis at f/3+paracorr? Thanks.




SGT, I will let you know. I will be using it with my SIPS system and will let you know how tight the stars are and how tight they are out to the edge of the field.


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5617661 - 01/11/13 05:50 PM

Thanks Bob.

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Sgt]
      #5618060 - 01/11/13 09:34 PM

SGT, It is too early in the evening to tell about my early exploits but I can tell you that the Leica ASPH is currently in my 20" scope in a 4x TV Powermate and the views of Jupiter, M42, and the Eskimo Planetary Nebula between 389x and 777x are pretty darn wild. The 2x Powermate that was limiting me to 389x was just not enough power for tonight. Finally, I get to really air this scope out! Bob

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5618320 - 01/12/13 12:47 AM Attachment (58 downloads)

The coyotes were literally howling, the owls were hooting and a Leica ASPH vario zoom 8.9-17.8mm with 60-80 degree AFOV got an intense workout tonight in my 20" f/3 Lockwood/JP Astrocraft. The NELM was just under mag 6 tonight as measured by my Sky Quality Meter and the seeing was quite steady. Earlier experiments tonight with the fans on Jupiter and Rigel showed that the (Comprehensive Boundary Layer Mitigation System) is working superbly. I tuned the SIPS to perfection on Jupiter using a 5x magnifying loupe and checked collimation of the scope after it had been cooling with the CBLMS running at full speed for about 1.5 hours. I was looking at Jupiter with the Leica ASPH and was finding that 194x was not even making the eyepiece or the scope breathe deeply. I popped the Leica ASPH into my 2x TV powermate and now was running views of the planet between 194x-389x. Still the views were showing that I could use more power. In goes the 4x TV Powermate coupled to the Leica ASPH for views between 389x-777x. Predominantly, the views at about 389x to about 600x showed periods where the planet looked like a CCD image. The orb of Jupiter seemed suspended in black space. The contrast of atmospheric features against a jet black background was jaw dropping. Now, for the first time since this past years WSP in the Florida Keys, I was able to view comfortably at over 550x. With the ASPH in the 4x Powermate and a 2" OIII filter, I had the scope go over to the Eskimo Planetary Nebula in Gemini which is an object on good nights that can take a lot of power. The Eskimo was not to disappoint either then or hours later at ridiculously high mags. I am used to viewing it with my former 28" f/3.5 Lockwood/Starmaster and so noticed that the brightness was way down with the OIII filter and only 20" of aperture compared to the views I would get with the 28". Now, I had not had a chance to see the Horsehead and Flame Nebulas with my new scope. I put a 2" H-Beta filter into the bottom of my ASPH and was zooming in and out on the Horsehead and Flame Nebulas. I actually like the view better in my Leica at 17.8mm with 60 degree AFOV than my 21mm Ethos or 17mm Ethos with the h-b filter and their 100 degree AFOV.

Of course, in the high mag mode, I had to see the Pup in Sirius. Sirius was a superb pinpoint of a star and I used it for further high-mag testing of the primary mirror. I did a test of the fans on this object and each time I turned off the CBLMS, the star would get more flairs. The tightest views were with the CBLMS running and so it was left on all night. Back to Jupiter with the 389x-777x eyepiece arrangement and Jupiter was strutting the GRS along with beautiful festoons and white ovals and a dark barge or two in the NEB. The amount of different colors I was seeing in the GRS, festoons, ovals, barges and belts was very impressive. At between 550x-777x, I was able to make out reliable but faint albedo markings on Ganymede in what I think was the Southern half of the Jovian Moon. This is only the third time that I have been able to do that and it was best seen when I moved Jupiter out of the FOV. I forgot to mention that I used the ASPH with the 4x Powermate on M42 and was seeing the A-I stars (not the H-stars). The G and I stars were only intermittently seen with averted vision. This is only the second time that I have seen the I and G stars without my image intensifying eyepiece. BTW, I tried my Micro IIE Gen 3 image intensifier and was unable to get it to come to focus with the SIPS system in place. I was lacking just a bit of infocus. I finished off the session tonight first returning to the Eskimo and seeing his face briefly with a full parka surrounding his face and nose. I then went back for a last look at Jupiter and the seeing was getting a bit soft even at a lowly 389x. It was time to wrap it up and glow in the aftermath of my best viewing session to date with my new telescope. It also represented the best magnification I was able to successfully deploy in the past year here in North Florida. For some reason, obtaining 1000x plus nights like we used to get have been very difficult for the past two years. I did some high-power testing of the mirror on Sirius and Betelgeuse and the mirror is superb! Mike, I found that the Leica showed pinpoint stars to the edge with tighter star points when it was in either the 2x or 4x Powermates with those items behind the SIPS. Without a barlow, the stars were a bit less tight and not so uniform across the FOV with just the Leica ASPH and the SIPS. The views were not bad but just not perfect like they were with barlowing. I am including a picture of the setup. You will note that all focusing was done with my 3" Feathertouch optional focuser wheel which made focusing a dream. I cannot say enough good things about this 3" focuser wheel for critical focusing at high-mags. To say that I am pleased with the scope and the performance of the Leica ASPH with the TV Powermates would be an incredible understatement. I am frankly ecstatic! I am very much questioning if I need all of my fine Ethos ep's (I have the whole set). As some know, I had done comparisons of the Leica ASPH with my Zeiss Abbe Ortho II's along with a host of other orthos and ep's and the Leica was a good as or at times better than the Zeiss glass and this is no small accomplishment. It's performance on Jupiter was so convincing tonight and the fact that it was being used in a f/3 scope with a Starlight Instruments Paracorr System (SIPS) that made the AFOV perform like an f/12 scope leads me to wonder how much glass I need? I am forever indebted to John Pratte for making such a stout scope with an ultra-stout focuser board/UTA that easily handled all of the weight placed on it. This is without a doubt, the finest 20" scope I have ever been priviledged to be the steward of. Bob

Edited by Bob S. (01/12/13 09:26 PM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5618969 - 01/12/13 12:20 PM

Bob, all I can say is wow.

Things have sure come a long way since I bought these 20" f/3, 1.25"-thick Pyrex blanks back in 2006. I could never have forseen what they have become.

Thanks for your report, and for trying a lot of things that most people would not.


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5619150 - 01/12/13 02:11 PM

Very nice report Bob, keep them coming.

There are times that miss the views from a large apeture scope. I remenice when I had my 20" SM and would scan the the night sky and I kept bumping into these obscure little galaxies, and I'd check my sky atlas to see what I was seeing. Not to mention how different and in your face the "eye candy" DSO looked compared to my smaller apeture Apo's, just one word, WOW!!!

The only thing I don't miss is the size and weight of that scope, and the hassel of using a ladder, setting it up and tearing it down. But not in your case, with the fast F/ratio keeping yor feet on the ground and those superb optics and the abilty to customize your scope. Between your posts and advise, and looking thru some of my freinds large apeture, fast F/ratio with top of the line optics like yours, and the lighter overall weight and portabilty of these scopes have made me belive in these type of reflectors. For me it has always been a case wanting the sharpest veiws with ease of use and portabilty. In other words "The juice had better be worth the squeeze". In this case you and others like yourself have proven this. I can't wait to get my 16" Spica Eyes scope!!

Nick T. :-)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5619221 - 01/12/13 02:58 PM

Hi Bob,
How does the 5X loupe help you for sips adjustment? How do you use it and are there other uses, i.e. collimation? Sounds intriguing.
Thanks for the ongoing reports and insights!
Jonathan


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: SACK]
      #5619308 - 01/12/13 03:44 PM

Congratulations on the fine results. You have a special telescope there my friend.

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: SACK]
      #5619349 - 01/12/13 04:06 PM

Quote:

Hi Bob,
How does the 5X loupe help you for sips adjustment? How do you use it and are there other uses, i.e. collimation? Sounds intriguing.
Thanks for the ongoing reports and insights!
Jonathan




Thanks for the kind words Mike, Nick and Doc. Jonathan, the 5x loupe is a large magnifying glass that I used to increase the image size of Jupiter on the SIPS cellophane tape method to determine when the SIPS was resolving the object perfectly at the focal plane. By using an image magnifier, I can better discriminate the focus on the tape and when the SIPS is tuned to the correct position to provide optimum coma correction for the eyepieces. If you look at the image on the cellophane without magnification, I think it is harder to discriminate when the SIPS is turned in/out just the right amount. When I find that perfect focus point, I then can lock in the SIPS and then check to see that I have not drifted off that perfect spot. It usually takes a time or two to properly tighten the SIPS without degrading the image just a touch because you are dealing with a tightening ring and also rotation of the focuser to lock it in place. As Fast Mike pointed out, he can then use his 17mm Ethos to establish where the best focus is with the eyepiece projecting the target instead of the cellophane tape on the SIPS adapter tool. I measured the distance from the back of the SIPS lens to the edge of my SIPS focusing tool and it was exactly 55mm for my scope. From now on, I can just use that figure to set the distance and not worry about any of the other shenanigans. Simplicity is why I bought the SIPS and I do not want to have to be fiddling with it very often. Bob

Edited by Bob S. (01/12/13 04:09 PM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5619401 - 01/12/13 04:36 PM

Bob, I would also like to add my thanks for your reports. I imagine I will need hands on with my own scope to sort out Mallincam. That's the joyful experimentation. First I need to take delivery of the telescope. Been a long wait.
Look forward to further reports.


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Busguy]
      #5619467 - 01/12/13 05:14 PM

Thanks for the report Bob!

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5619596 - 01/12/13 06:27 PM

Quote:


I measured the distance from the back of the SIPS lens to the edge of my SIPS focusing tool and it was exactly 55mm for my scope. From now on, I can just use that figure to set the distance and not worry about any of the other shenanigans. Simplicity is why I bought the SIPS and I do not want to have to be fiddling with it very often. Bob




Bob, an additional question. In this position SIPS, you adjust the focus with the Ethos-17?


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: a__l]
      #5619640 - 01/12/13 06:52 PM

Quote:

Quote:


I measured the distance from the back of the SIPS lens to the edge of my SIPS focusing tool and it was exactly 55mm for my scope. From now on, I can just use that figure to set the distance and not worry about any of the other shenanigans. Simplicity is why I bought the SIPS and I do not want to have to be fiddling with it very often. Bob




Bob, an additional question. In this position SIPS, you adjust the focus with the Ethos-17?




No at 55mm out, the SIPS is properly focused for my telescope. The 17mm can then be a reference for where it comes to focus best. It is takes about 1/2 turn of the fine focuser to get it to come to focus for Fast Mike's scope. I am not exactly sure with the arbitrary 55mm that mine is out how much more outfocus the 17mm Ethos will demand to come to focus? Bob


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5619669 - 01/12/13 07:08 PM

A very interesting topic of conversation came up on the Yahoo Lockwood Mirror site concerning my temperature management system dubbed a CBLMS (Comprehensive Boundary Layer Mitigation System). Mike Lockwood advised that for many years he has noticed that the sea breezes at the Winter Star Party in the Florida Keys seems to help many of the Newtonians to perform at higher levels than might be expected elsewhere. Mike suggested that the ability to cool the mirror from all sides that the sea breezes provide may be a large factor in mitigating other temperature-related variables such as body temp, ground temperature, scope materials that may be deleterious to the microcosm of an environment just above the surface of the primary mirror. Lockwood advised that his 20" f/3 that is also 1.25" thick seems to perform better when the breezes kick up a bit at his prarie location. He does not have fans on his 20" f/3 Starmaster and appears to have noticed beneficial effects from the entire mirror being bathed in constant temp air. I hadn't thought this completely through before but I suspected that ground heat and certainly body heat could affect the seeing environment inside our Newtonian telescopes. Daniel Mounsey has been a very strong advocate for the degradation caused by scope positioned down wind from our hot bodies. It also makes great sense to me that head radiating from below the scope would not benefit seeing and that is why scopes set up on cool grass as opposed to hot concrete/asphalt seem to perform better. Wow! This is an interesting turn of events. From my early data, there seems to be little doubt that the CBLMS is additive and much more so with both fans running simultaneously. Bob

Edited by Bob S. (01/12/13 07:14 PM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Busguy]
      #5619671 - 01/12/13 07:09 PM

Quote:

Bob, I would also like to add my thanks for your reports. I imagine I will need hands on with my own scope to sort out Mallincam. That's the joyful experimentation. First I need to take delivery of the telescope. Been a long wait.
Look forward to further reports.




If I understand correctly, the spare travel for Mallicam is 6 mm (with unknown settings SIPS).
Further, an additional limit of 10 mm height spacer + 1.25/2" adapter (height not known). It is not known whether the set HDX2-F kit (camera XTREME), the limit may be higher.
If replacement mode 1.25 to 2" (new 2" Focuser Dob Adapter for Mallincam - $ 89.99) get spare travel 10+6+(?) mm (minimal).
Since the field Mallincam little, there is a chance to try MFR-3+10 mm spacer (travel 14 mm).
But! All these issues need to be clarified with the manufacturer Mallincam.


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5621886 - 01/13/13 11:07 PM

In comment to Bob's most recent post, what is important here is that now the conditions are present/satisfied that allow very fine differences in performance to be discriminated.

With 1) good optics, 2) good mirror support (edge and back), 3) good collimation, and 4) good equilibration made possible by the fans and thin mirror, the scope is performing up to the potential of a quality 20" visual instrument.

The conventional technique of blowing air on the back of mirror will help for a while, but it causes an uneven temperature distribution in the mirror and eventually when the mirror does cool it starts pulling the warm air off the ground back up into the mirror box. The cooling system in the 20" f/3 avoids that, and cools all sides of the mirror much more evenly, something that I have recommended for years to those that have asked me. Even cooling is vital for the ultimate performance on most nights. While one may get lucky with conditions on a few nights a year, with a cooling system like this there are going to be a lot more of those amazing nights.


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Mike Lockwood]
      #5630722 - 01/18/13 10:32 PM Attachment (80 downloads)

Finally, Even with seeing being 5/10 (Jupiter was boiling even at low mag) and a half moon about 35 degrees away from the Horsehead Nebula, I was able to finally deploy my Mallincam Xtreme connected to my integrated laptop computer in the 20" f/3 Lockwood/JP Astrocraft telescope. I was able to get very good images up to 65 second exposures which is unreal! I am including a screen shot of the control center values for the Mallincam and then an unretouched photo of the Horsehead nebula displayed on my 3.5" Watec monitor with a 55 second integration.

Edited by Bob S. (01/19/13 07:36 AM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5630725 - 01/18/13 10:34 PM Attachment (70 downloads)

Here is my poor photo of the Watec monitor and a 55 second integration on the Mallincam. I was able to use the MFR-3 and a 5mm spacer and was able to keep the SIPS system in place. I had to rotate the SIPS system in about 4 complete rotations to get the Mallincam to come to focus with a little infocus left (about 1/2 turn of the fine focuser knob on the Feathertouch). BTW, I left the Comprehensive Boundary Layer Mitigation System on at their lowest speeds and the fans being on another circuit did not seem to affect the Mallincam images on the monitor.

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5631115 - 01/19/13 07:32 AM Attachment (69 downloads)

Here is a closeup of the Mallincam Xtreme in the focuser and you can faintly see the Horsehead Nebula on the Watec screen with my handheld camera's flash wiping out most of the percept you are seeing (you can see the star field and better image without the flash in the post just above this one). The extra dangling cable is a connnector for a Baluns that would allow S-video output that is remotely located on the side of the mirror box that can then run out to a larger monitor or be the terminus for a wireless transmitter. Those features will be utilized further down the line. I am absolutely delighted that another proof of the concepts we integrated into the scope are bearing fruit. As many of you ATM'ers know, you do your exhaustive homework, think and re-think all of the various components and then roll the dice. I also need to do a serious shout out to Gary Myers of ServoCat for producing a drive system that has allowed me to get round stars on the Mallincam with 65 second integrations. I am not sure what the upper limits are yet on the whole system? Thankfully, we did not roll "snake eyes" last evening

Edited by Bob S. (01/19/13 05:07 PM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5634036 - 01/20/13 10:19 PM Attachment (60 downloads)

Well, This is my last installment for a while. Getting bilateral cataract surgery this coming week with one eye done on Wednesday and two weeks later the other eye that will take me out of viewing for about a month. Hopefully, I will get back a bunch of blue spectrum perceptual capability that will allow me to play in the Calcium-K band with my solar scope. However, tonight, I played with the Mallincam Xtreme and a MFR-6 with two 10mm spacers and a 1.25" nosepiece and had a lot of back focus capability. As some of you know, the MFR-6 is the back lens of the MFR-5 ensemble that was designed for SCT's. When I tried the MFR-3 with a 5mm spacer, I had very little backfocus available. The MFR-6 with two 10mm spacers and the 1.25" nosepiece seem to be the best bet. In all cases, the SIPS system was turned all the way in to allow for adequate focus capability. If you compare the picture of the focuser positions with the Mallincam on the Horsehead and the MFR-3 with 5mm spacer, you will not that it is almost fully racked in. In the second picture below with the Crab Nebula and the MFR-6 with 20mm of spacers and the 1.25" nosepiece, the focuser is racked out probably about 8-10mm. The view below is of M1, the Crab Nebula only about 20-25 degrees from a more than half full Moon moving up toward zenith with a 50 second integration of the Mallincam. The pinks, whites and tendrils of the Crab were a bit washed out with so much Moon out but it was still a very pretty sight.

Edited by Bob S. (01/21/13 10:02 AM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5634039 - 01/20/13 10:21 PM Attachment (51 downloads)

I also decided to play with the various preset settings on the Mallincam control software and looked at M42, the Moon and Jupiter. Here is a picture I took of the Moon displayed on the Watec. I am favorably impressed with the strides Mallincams have made on lunar/planetary objects. Carl Wright here in Florida has been getting phenominal images of the planets with his 22" Starstructure for years but he had to learn how to play with the settings. The presets make it easier for us less ambitious folks.

Edited by Bob S. (01/21/13 08:24 AM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5634044 - 01/20/13 10:24 PM Attachment (59 downloads)

And finally, a 3 (three) second integration of M42 with M43 peeking out with the very fast speed of this telescope coupled to the focal reducers. You can see that the Trapezium in Orion is blown with only a 3 second integration. You can also see the ethereal view of the nebula as you get a sense of flying into the center of the stellar generator. The camera control software is new to me so I was not facile enough to fool with the gain and tone down the exposure in the time alloted for what I wanted to do on my last night out for a while. Well, it has been a lot of fun helping to prove the concepts that John Pratte, Mike Lockwood, Gary Myers and myself put together. I also want to say a big thanks to Joe Wambo, Jimmy Lowery, Mara Da Lio and many others who helped make this 20" f/3 a real jewel of a scope. The telescope is working exceptionally well and it will be providing years of fun and enjoyment. I really look forward to sharing a lot of fun views with others. The only problem is that the telescope is so darn beautiful to me that I am going to have a hard time ever wanting to move it away from the confines of my property to darker sites and risk putting dings in it

Edited by Bob S. (01/20/13 11:12 PM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5634106 - 01/20/13 10:59 PM Attachment (51 downloads)

Sorry that this thread has been so long but you know how it is when you get old. It takes forever to complete a few tasks, let along tell a bit of story about a scope's adventures.

Edited by Bob S. (01/20/13 10:59 PM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5634217 - 01/21/13 12:30 AM



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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Project Galileo]
      #5634288 - 01/21/13 01:35 AM

Bob been reading this thread for quite a while and it's been an adventure! Best of luck with the surgery.

CS,

Nicos


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5634332 - 01/21/13 03:31 AM

Quote:

However, tonight, I played with the Mallincam Xtreme and a MFR-6 with two 10mm spacers and a 1.25" nosepiece and had a lot of back focus capability.





Bob,
What is the total length MFR-6 + 10 Spacer+ 10 Spacer + 1.25" nosepiece?
Risk of contact lens paracorr?


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: a__l]
      #5634461 - 01/21/13 08:12 AM

a____i, From the tip of the 1.25" nosepiece to the base of the ensemble where it butts up against the brass retaining ring that keeps the chip in place on the front of the Mallincam is 42.5mm. I also used it with only 1 10mm spacer in the 32.5mm mode. Did not seem to make much of a difference between using one or two spacers. I know it changes the focal reduction but on the little Watec screen, it did not seem to make much of a difference. Nicos, I wish I could have views that you are going to get with your new Sumerian 12" telescope on your lovely island. Thanks for the kind thoughts. Bob

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5634905 - 01/21/13 12:49 PM Attachment (33 downloads)

Bob nice scope! Also, good luck with your surgery. Is that a heated eyepiece box I have circled in your pic?

Cheers,


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Scanning4Comets]
      #5634915 - 01/21/13 12:56 PM Attachment (33 downloads)

Markus, No, that is the cork-lined telescope control center that houses a laptop, Argo Navis DSC's, laptop dew heater for the screen, wired handpad and wireless hand pad with receiver underneath the control center housing. It also connects to the Mallincam via a USB port and has a planetarium program that will run the telescope. The orangish Kendrick laptop heating pad actually goes behind the back of the gorilla glass screen on the laptop. The Dell XPS13 has a solid state hard drive that I think has a 500 gig capacity and no moving parts. I purposely put it on the opposite side from where I am viewing so it does not interfere with seated or standing visual observations and also throws any light away from the telescope. The control center is on a stalk that is totally internally wired and easily removable and derives its power from the one input from my 102 amp/hour marine battery that goes into the powered ground board with one 15 foot long thin cable. The stalk also has a power transformer built in that supplies the proper power requirements to my laptop as well as the Argo Navis. What is really neat about the system is that with the wireless handpad, I can do my two star alignments and use the GOTO button to enter button presses into the Argo Navis without physically having to be at the AN. The only battery on the telescope is in the Telrad but the Telrad reticle is heated by part of the internal wiring system. There are three individual electrical circuits in the scope (1= fans/dew heaters systems 2= ServoCat power sources 3=camera power supplies). The systems were isolated to prevent radio frequency noise from interfering with the Mallincam camera system/display. When I am at the eyepiece, if the object is not exactly centered, I have the ability to slew the telescope with the ServoCat III system at four different slewing speeds. It also has two speeds for spiral search. Additionally, the whole system has two overall speed settings for all of the individual functions. It was a good thing that John Pratte is really up on electronics although he is a chemical engineer by prior training. Bob

Edited by Bob S. (01/23/13 05:31 PM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5635178 - 01/21/13 03:12 PM

Awesome Bob!

Cheers,


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Scanning4Comets]
      #5635377 - 01/21/13 05:14 PM Attachment (103 downloads)

Markus,
I realized that the photos of the JPA control center were not very good and were taken at a time during the construction phase. Here is a current picture showing the control center in relationship to the entire telescope (the focuser and other controls are exactly on the opposite side of the telescope). The control center fabrication was a pretty involved process that took Pratte about three days to construct. You can also see one of the two powered-groundboard connection points below the rocker box and there is another connector on the other side of the scope in a foot so dependending on where I plan to spend most of the night viewing, I can keep the power cord well out of the way. One of my main criteria was to minimize any dangling wires.

Edited by Bob S. (01/21/13 07:21 PM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5635387 - 01/21/13 05:17 PM Attachment (86 downloads)

Here is a close-up of the quick disconnect plugs that allow the control center to be de-mated from the telescope in less than 5 minutes. It is supported by two attachment points and is relatively stable/sturdy. All of the connections are either color coded or have specific sized plugs that cannot be inadvertently interchanged. The connector on the side of the mirror box is where the S-video output is if I want to relay the image to a larger external monitor. I have been thinking about installing a transmitter coming off the S-video output plug and then simply have to hang the receiver on whatever viewing source I want the signal to be displayed on. What is also very cool is that John Pratte rigged up a set of wheelbarrow handles that can attach to the scope utilizing the wheels and also attach with the control center in place. There was not much left to chance thanks to his forward thinking on each component and how it was going to be integrated into the scope. You can see where the captive bolts on the wheelbarrow handles attach to the rearward part of the rockerbox. Bob

Edited by Bob S. (01/21/13 06:29 PM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5635454 - 01/21/13 05:59 PM

A true DREAM MACHINE!!

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Starman81]
      #5636061 - 01/22/13 12:58 AM

All those exposed wires and components make me nervous- I'd probably kick it or get tangled in it somehow- ever think of creating some kind of small protective cover? Might get in the way of the bearing...

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: PureHeaven]
      #5636314 - 01/22/13 07:10 AM

Quote:

All those exposed wires and components make me nervous- I'd probably kick it or get tangled in it somehow- ever think of creating some kind of small protective cover? Might get in the way of the bearing...




Frank, It does look like an electrical grid and when I first saw it, I had to have John Pratte explain each and every wire to me so that I knew what was going on. The nice thing about the location of the wires and the control center is that it was designed to be used standing. With the height of the hood and clearance away from the scope I don't think it will suffer much, if any punishment. Pratte even made a slight tilt in an aluminum drip channel on the rear of the hood at my suggestion that directs any condensation away from any of the electronics and falls harmlessly to the ground on only one side of the channel. The other side of the drip channel is blocked off to prevent any moisture from dripping onto the electronics. As is with any of our telescopes, the electrical systems are pretty much hardened and selected to function in a pretty wet (dew) environments which we definetly have in Florida many months of the year. My current challenge is to have AstroSystems make a custom cover so that the scope can stay out in the daylight during those times that I have it deployed in the field for numerous days under our hot Florida sunshine. Bob

Edited by Bob S. (01/22/13 08:47 AM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5644896 - 01/26/13 06:47 PM Attachment (66 downloads)

I have been asked what we used for a sucking fan on the rear portion of the mirror box. It is a Sunon Mag Lev fan that is about 4.5x4.5" and says that it has a minimum 127CFM. The fan is only about $22 mail order. I am not sure if that CFM rating applies when I turn down the potentiometer to it lowest setting before the fan stalls which is how I have it set when viewing. Of course I have it up at full sucking speed along with the front blowing fan when in the equilibration mode of the scope. I do not generally view with both fans blowing/sucking at full speed although the images still seem better than if the mirror is hot and radiating thermal plumes. This suggests to me that the fans system coupled with the annulus is not producing turbulence to such a degree that the images are being terribly perturbed and I keep the AstroSystems shroud up a couple of inches from the mirror box during this phase of active mirror cooling. Here is a picture of the fan. I will then show a detailed view of the rear of the mirror box.

Edited by Bob S. (01/27/13 03:01 AM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5644905 - 01/26/13 06:52 PM Attachment (67 downloads)

Here is the Sunon Mag Lev fan encased in the Sorbothane and surrounded by a solid metal backing plate than encloses the entire mirror box to create the necessary suction and increase the efficacy of the annulus in front of the primary. The reason we used the magnetic levitation fans was that they have an excellent reputation for having very low vibration and have long-life endurance. On the right upper portion of the picture is the potentiometer and just to the right of that is a little red switch that turns the fan on and off. The two bright screws in the upper portion of the mirror cell frame are the built-in contact points that power the rear fan unit when the enclosed mirror cell is installed. I used the switch to test the efficacy of the rear sucking and front blowing fan of the Comprehensive Boundary Layer Mitigation System (CBLMS) running seperately and combined. To date, the scope has shown more detail visually on Jupiter with both fans running at their lowest speeds than either one fan (front or back) or no fans running.

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5645570 - 01/27/13 07:46 AM Attachment (66 downloads)

I was asked about collimation of the scope with the front boundary layer blowing fan. The blowing fan is a Sunon MagLev KDE1207PHV1 which measures 2.75" x 2.75" The entire front fan ring that rides on 4 Sorbothane pads can be removed by turning two keeper tabs and disconnecting the RCA plug from the power source on the top of the mirror box. Alternatively, the scope can be slightly tilted and the front boundary layer fan can be lifted up and tilted out of the way to collimate the scope. As previously mentioned, the fan is run on high with the potentiometer for cooling or when the mirror is warm and then is run at its slowest speed when the primary is equilibrated.

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5645575 - 01/27/13 07:55 AM Attachment (81 downloads)

And finally, the requester wanted to see the relationship of the front fan to the primary and the annulus. The front fan is approximately 9" above the primary. The annulus surrounding the primary is approximately 1/2" larger in diameter than the 20" 1.25" thick Lockwood primary and approximately 1" above the primary and appears to be effectively creating a venturi effect that Mara Da Lio discussed. We chose to have the annulus closer to the primary than Da Lio had articulated because we have the front blowing fan. In tandem with the rear fan, the mirror appears to uniformily equilibrate. As some of you will remember, when we used the rear sucking fan and the annulus only, the mirror tended to become overcorrected due to the excessive cooling of the outer portion of the thin mirror according to Mike Lockwood as he inspected the initial performance in the field under the stars. The front fan blowing on the front of the mirror appears to gently scrub the boundary layer surface and the rear exhaust fan appears to laminarly remove the air rather than it being trapped inside the mirror box in the front of the primary mirror surface. We coined the term Comprehensive Boundary Layer Mitigation System or CBLMS which is a pretty ambitious moniker but seems to be living up to its billing. John Pratte is retrofitting his 25" f/4 Lockwood/JP Astrocraft and may have it completed in time for the 2013 Winter Star Party in the Florida Keys. If you get a chance, check out the scope's performance if you happen to make it there this year. The front fan is in the shadow of the 5" secondary and the support wires are oriented identically to the secondary spider to reduce any further diffraction spiking. You can also see that the primary mirror lower edge supports on the right side of the picture have teflon roller ends which allow the primary mirror to move freely in all positions without the risk of binding.

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5664587 - 02/06/13 02:16 AM

It appears that partial implementations of the CBLMS are bearing fruit for others. JohhnyHa said this on another thread yesterday: "Update: Last night using my new exhaust system on my mirror box, I had the best views of Jupiter ever in my lifetime. So it certainly isn't hurting to switch to the exhaust fan. I was able to go over 250X for the first time in months and months, with a perfectly stable, sharp image. I have never seen such detail on the disc, it was simply amazing. I was truly gobsmacked, I did not think my scope was capable of such incredible views from my backyard in Los Angeles. I recently switched to a thinner 14.5" Zambuto mirror and Protostar quartz secondary, and that combined with this new exhaust fan system has delivered the goods - finally - a beautiful, thermally stable image.

This is a simple 3 speed exhaust fan with a closed back, I don't have a di Lio baffle or any boundary fans installed at this point. I also had my 12V box fan about 8 feet from the scope creating a light breeze blowing my body heat away.

--------------------
Johnny

FS152
15" Obsession Classic"

It is good to see others experimenting and developing additional empirical evidence for the concepts of a comprehensive boundary layer mitigation system's (CBLMS) potential efficacy. I hope Johhny, if he implements a front blowing fan, will have it suspended over the face of the mirror and be able to set the fans speed very low to not create unnecessary turbulence. The Mauro Di Lio annulus will likely also be a very helpful addition to Johnny's 15" Obsession. Also, imbedded in Johhny's report is that fact that he was using a very small fan to blow his body heat away from the Newtonian. Daniel Mounsey for many years has extolled the benefits of this procedure and it too is likely an additive factor in Johhny getting the best views he has ever had. John Pratte, owner of JP Astrocraft is currently down in the Florida Keys with his 25"f/4 Lockwood/JPA and is experimenting with a complete CBLMS on his scope this week. I asked him to do all of the switching on and off of the front boundary layer blowing fan as well as the rear enclosed mirrorbox sucking fan to ascertain how the CBLMS works in very stable temperature conditions and what kinds of performance changes are noticed? Bob

Edited by Bob S. (02/06/13 06:07 AM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5664728 - 02/06/13 07:13 AM Attachment (67 downloads)

Thanks Bob, this thread has definitely inspired me to try out some new thermal solutions. Yours is a work of art!

On my 15" - I think the baffle on the top of the Obsession box acts somewhat as a di Lio baffle, at least in the sense that I feel it is creating a very laminar air flow around the mirror. It's about 9" above the mirror but I think it helps. The important variable that I have recently changed is the flow of the fan, from blowing on the back of the mirror to exhausting air from the box. I have also coupled this with closing up the back of my mirror box with Protostar flockboard, a kydex-like material.

The Flockboard is also flexible and (very important!) I have formed it into a scoop top and bottom (see photo) which helps pulls air from around the mirror.

The theory here is that an exhaust fan can gently pull the air from around the mirror, whereas a blowing fan cools the mirror faster but just creates turbulence in the box.

A small scrub fan placed above the mirror like yours Bob, is the obvious next step, along with a di Lio baffle - but meanwhile with the results I had last night I'll wait -...

Truss dob exhaust fans, unite!


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: johnnyha]
      #5665059 - 02/06/13 11:45 AM

Quote:

Thanks Bob, this thread has definitely inspired me to try out some new thermal solutions. Yours is a work of art!

On my 15" - I think the baffle on the top of the Obsession box acts somewhat as a di Lio baffle, at least in the sense that I feel it is creating a very laminar air flow around the mirror. It's about 9" above the mirror but I think it helps. The important variable that I have recently changed is the flow of the fan, from blowing on the back of the mirror to exhausting air from the box. I have also coupled this with closing up the back of my mirror box with Protostar flockboard, a kydex-like material.

The Flockboard is also flexible and (very important!) I have formed it into a scoop top and bottom (see photo) which helps pulls air from around the mirror.

The theory here is that an exhaust fan can gently pull the air from around the mirror, whereas a blowing fan cools the mirror faster but just creates turbulence in the box.

A small scrub fan placed above the mirror like yours Bob, is the obvious next step, along with a di Lio baffle - but meanwhile with the results I had last night I'll wait -...

Truss dob exhaust fans, unite!




Johnny, The idea that you are using a rounded rear baffle is an interesting wrinkle to the experiments. John Pratte and I toyed with and are still considerig some kind of a kydex ring around some part of the rear portion of the primary mirror to enhance the sucking effects of the rear fan. I have such a strong fan that it may not be necssary and with the variable potentiometer, I can pretty well control the velocity but do not know how much CFM I am actually exhausting?

Keep up the good work. As you have now found, the "juice is worth the squeeze". I suspect that the trick for closed tube fans is to adopt our same strategy for the rear enclosed sucking fan but unlike our larger Newtonian that can have a front blowing fan on the center of the primary, people may want to adopt a neat little device that has shown some efficacy in my 10" Portaball or just build in a small Mauro Di Lio annulus to create a venturi effect from the sucking fan? Much more work needed on those issues I am sure.

In the new PB, they are now installing a very tiny boundary layer mixing fan that is on a swivel base that is just above the primary mirror's surface. When I turn on this tiny little fan, it seems to gently mix the air on the surface of the primary. The effects are not nearly as dramatic as the CBLMS. I think it might be adantageous to reverse my cooling fan on the PB and use it to suck air out of the back of the ball. I have not given that much thought at this point. Bob

Edited by Bob S. (02/06/13 04:45 PM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5666674 - 02/07/13 09:10 AM

Bob - it looks like you got yourself one very nice scope!! Having a thin mirror has to help tremendously. My almost 2" thick mirror is often 6 degrees or more above ambient temperature, even when running a large fan on the back. iam working on an idea for a fan box that "may" help bring the temperature of the mirror down a little bit quicker. Again, very nice scope you have there!

Duane


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: DuaneS]
      #5667434 - 02/07/13 04:29 PM

Thanks for the kind words Duane. It was a fun labor of love on John Pratte's part as well as my own. Not to forget mentioning that Mike Lockwood said he nailed it on the 20". Of course, your 30" scope is a real performer and getting that large slab of beautifully figured glass to equilibrate has to be a challenge. I have gotten reports from John Pratte that Joe Wambo's 32" Lockwood/Webster is really smoking down at the WSP in the Florida Keys this week and he of course has the front fan in the shadow of the secondary which is very much like my front fan unit and was the prototype for my fan. Of course they are not experiencing more than about 6-8 degree temperature shifts in a 24 hour period which makes things easier. Look forward to hearing what you do to get that big mirror equilibrated. Whatever you do, I would consider a front fan. It seems to really help with the views in Wambo's big scope and really is additive in my 20". The CBLMS that we developed is also based on the contribution of Jimmy Lowery who is cooling his big 48" with an enclosed rear mirror box and ten mag lev fans sucking the warm out of the back of the telescope while cooling his large mirror and apparently helping to scrub his boundary layer because he reports that it is always better to just leave the fans on. He says that just that application of fans in an enclosed mirror box greatly improves his images and he leaves them on all of the time. You might want to get in touch with him and see what he might recommend for you. I suspect that if you incorporated a fan system like Pratte designed that you would likely overcome most of your thermal issues? Additionally, Mike Lockwood and Mike Zammit could give you further suggestions I am sure. Bob

Edited by Bob S. (02/07/13 05:25 PM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5669175 - 02/08/13 02:26 PM

I talked with John Pratte this morning who is at the Winter Star Party in the Florida Keys with his 25" f/4 Lockwood/JP Astrocraft telescope and his newly installed CBLMS (Comprehensive Boundary Layer Mitigation System). He advises that so far, he has not seen any appreciable additive features of the CBLMS in the very steady temperatures. He said with the front fan blowing onto the primary and the rear fan sucking in the enclosed mirror box, the CBLMS does not degrade the image but is not currently additive.

This is a very interesting piece of the puzzle that we are piecing together. When he gets the scope back to Illinois, it will be intersting to see how much difference is made. We already know that on my 20", when we only had the rear enclosed sucking fan going that the images immediately cleaned up on a warm mirror but eventually led to an overcorrection situation because we were running it on high speed for several hours not having had any experience with it to that point, and no front blowing fan to equilibrate the mirror uniformily at that point in time.

Here in North Florida, with this rather temperate Winter we have been having, the CBLMS has so far been effective and additive with every single use. It may turn out that when the temperature differential falls to a certain point that it will not longer be effective? Only time and continued experimentation will tell the story. Bob

Edited by Bob S. (02/08/13 08:41 PM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5697533 - 02/23/13 11:05 PM

It was gratifying to see an astrobud's setup today where he adopted part of the CBLMS for his 12.5" RCOS Classical Cassegrain imaging telescope. He mounted 4 very tiny MagLev fans on each of the short truss poles with vibration isolation blowing toward the center of his primary and says that he runs the fans 24/7. He has found that the blowing fans on the primary keep his scope closer to ambient than he has ever gotten. He has an SBIG 11000 attached to the scope on a AP1200 mount and plans to take pictures with and without the front boundary layer fans running and then evaluating the spot sizes of the photos. I can't wait to see the results of this experiment. The scope has the integrated rear sucking fans that are used for cooling the primary. Hopefully, at some point, I will try and convince him to put a control on the rear fans and bring them down to a slow speed to see if the comprehensive boundary layer mitigation system concept enhances his photos. He was mentioning that he can start and run the very tiny MagLev fans at 2.3 volts. My buddy Joe has taken many published deepsky photos and it will be interesting to see what tricks lie ahead for his advanced setup. Bob

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5823645 - 04/26/13 06:15 AM Attachment (45 downloads)

Life has a way of distracting you from the things that really matter. I had a fellow named Josh Balsam who had built me a portable Bahtinov mask for my 20" JPA to get critical focus with my Mallincams or DSLR's to consider making me an apodizing mask. Carl Wright, an observer at CAV has extolled the benefits of apodizing masks for years and I decided that it was time to have my own. Josh utilized the scheme presented by one of the club members of the Colorado astronomical society and it arrived a few days ago. Last night with an almost full moon and Saturn close by was the perfect time to test out the apodizing mask. I did at least x6 A/B comparisons of the planet with and without the apodizing mask in place. 5/6 times, the image of the planet was sharper with the prismatic/psychedelic apodizing mask in place. I used my Leica ASPH zoom to get just the right amount of magnification to get the sharpest images when doing the comparisons for the slightly varying seeing conditions. I was also using the Comprehensive Boundary Layer Mitigation System with both front blowing and rear sucking fans working at their lowest speed to increase the sharpness of the image. The results were very pleasing and I can't wait to try it out on double stars. Suiter and others discuss the benefits of apodization. It appears to need at least 10" of aperture or greater to accomodate the reduction of light to the primary. Great fun and Saturn was showing very sharp ring detail but more interesting planet atmospheric detail/color than I am accustomed to seeing. Bob

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5824096 - 04/26/13 10:54 AM

This threat keeps getting better and better.

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Project Galileo]
      #5825733 - 04/27/13 06:23 AM

Galileo, I suspect you meant thread but in a sense, this telescope is a "threat" to those unidentified tiny points of light far far away.

Last night, the seeing was predicted to be good and I wanted to further explore the benefits of my new apodizing mask with Saturn as the target. I rolled the scope out onto the mat it sits on to prevent thermals from the driveway after having stored it in the cool garage all day. I collimated it to perfection, turned on the CBLMS and then tuned the Starlight Instruments Paracorr System (SIPS) using my 17mm Ethos with the focuser backed out from the bottom 1/2 fine focuser turn and then rotated the SIPS until the stars were hard points of light. This particular procedure turns out to be easier than the manufacturers suggested procedure because I developed it after talking with Fast Mike who has a 28" f/2.75 with the SIPS and after following their procedures for setting the SIPS and found where the 17mm Ethos comes to focus. Sort of a reverse engineering technique which works well and does not require use of cellophane tape and supplied tube, etc. to tune the built-in Paracorr system. I then did my two-star alignment using Pollux and Arcturus and then viewed a couple of galaxies before Saturn and the Moon came up. I then pointed the scope at Saturn which was low and found that the views were mediocre. I had used my Leica ASPH variable zoom 8.9mm-17.8mm to align the scope and had it in about the 10mm position. I did an align on Saturn and went in for about an hour and watched some TV and napped a bit. When I came back out, the scope still had Saturn in the FOV. Did I mention that I love the ServoCat and performance of the JP Astrocraft telescope for the great precision and orthogonality?

I viewed until 1 a.m. EDT and the seeing appeared to get to 8.5/10 or better. I kept the apodizing mask on constantly while viewing Saturn to get the most possible contrast I could get. The ASPH ran out of magnification so I added a 2" 2x TV Powermate and placed the ASPH in it so I now had mag from 4.5mm-8.9mm. This translated to 1753mm of focal length with the 1.15x magnification factor of the SIPS device and mags of 197-394x in the range of the zoom ep. In the last hour of viewing, I was primarily using about 350-394x and with the apodizing mask, the contrast features on Saturn were pretty spectacular. I had studied Christopher Go's recent images of Saturn from the Phillipines and was trying to tease out visually as much as I could knowing what features Christopher had captured with his camera. The views were intoxicating.

During this time, I also got to wondering how my other eyepieces would stack up against the Leica ASPH with the apodizing mask in place. I used a TV 4.7mm Ethos, UO 7mm Ortho and 5mm Pentax XW in my 2x Powermate. If you reverse the order of listed ep's, you will note that in my very fast f/3 telescope, the Ethos put up the poorest image of Saturn with the colors rather muddled and poor resolving capability followed by better views but not great with my 7mm UO Ortho in the Powermate. The 5mm Pentax XW showed the second brightest image and the amount of detail was the best of the "also rans". The Leica ASPH was so absolutely superior for light throughput, neutral color and resolving ability in the Powermate that it was not even a contest. I was very surprised at how poorly the 4.7mm Ethos compared with all the variables in place to all of the other ep's. I love that ep for widefield stellar views as one of my favorites but on this night with my fast scope, relatively newly operated on eyes with crystal clear lenses in place following cataract surgery, the Ethos really did not perform up to any of the other ep's?

Well, I was absolutely delighted to spend the better part of the last hour going between 350x-394x with the Leica ASPH and my new apodizing mask. It was intoxicating and I really did not want to go to bed but have a busy day planned and so had to balance play with other pursuits.

The fast Lockwood mirrors and all of the supporting systems provided the best views of Saturn that I have experienced with this new scope. I am really hooked on the use of Josh Balsam's superb apodizing mask that was patterned after the Colorado groups build instructions. What a wonderful contrast booster! Bob

Edited by Bob S. (04/27/13 06:35 AM)


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5926872 - 06/18/13 06:15 AM

The 20" f/3 Lockwood/JP Astrocraft continues to follow on its journey's through space now via computer control. I recently installed Software Bisque's Sky X Pro planetarium software and this morning at 3:30 a.m. EDT was able to successfully slew to objects displayed on my 12" notebook computer via the Sky X program that is nicely tucked into the hooded control stalk that is located on the opposite side of the focuser. I first looked at M57, then M22, followed by Neptune and then M27. The Veil Nebula was up in Dobson's hole and the scope's limits would not allow slews to this area. I disengaged the drives but continued to use the Sky X to navigate to the Veil via the computer and hand movement of the scope and then hand tracked all around with a 31mm Nagler with an OIII filter in a Paracorr II. The views were beautiful!

Getting control of this instrument with a planetarium program was part of the initial build parameters and this goal has finally been achieved. My next adventure will be to not only control the scope with the Sky X but also toggle the computer screen to also control my Mallincam Xtreme astrovideo camera that outputs to a Watec screen on the UTA at the same time. The whole concept of fully integrating many different complex systems into one complete package is becomming a reality. Bob Schilling

Edited by Bob S. (06/18/13 06:27 AM)


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astrocrafter
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #5976485 - 07/17/13 05:53 PM

After Bob's enthusiasm over his CBLMS fan system on the 20" I built him, I had to modify my 25" f/4 Lockwood with a similar front/rear fan system.
I first tried the new arrangement at the WSP but couldn't tell much of a difference with or without the fans. I suspect the constant breeze and relatively constant temperature prevented much of a boundary layer from forming.


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astrocrafter
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: astrocrafter]
      #5976500 - 07/17/13 06:01 PM

My second trial was over this last weekend. I used antares as a target and compared how much of the time I could get a clean split with no fans, front fan only, or both fans. It appeared to give the best results with both fans running but it was nothing dramatic. The seeing overwhelmed the boundary layer effects. Again the nightime temperature drop was minimal. I'll continue to test and refine the system and report the results. There's a lot of variables to consider. I'd like to see how the system reacts to dropping temperatures.
John Pratte


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: astrocrafter]
      #5976878 - 07/17/13 09:48 PM

Hi, John Pratte,
Well, as you know I have the mini version, the Sweet Sixteen 16"f/4, which in my case has Sky Commander and a fan and a Paracorr but no automatic drive. I love this scope and recommend it highly to anyone considering a 16" scope, the views are great and the scope works beautifully.

I am big fan of short focal length scopes that can be used sitting down. I saw a drawing of one, many years ago in the frontispiece of the three volume Amateur Telescope Making, and was hooked immediately; that drawing appeared to be about a 10" f4 or so. It made sense to me immediately, much more attractive than long Newtonians or refractors.

And the book, Telescopes for Skygazing, by Dr. Henry Paul, had some photos of his friend George Keene's 12" f/4.3, which was considered very radical indeed in those days when focal ratios shorter than f/7 were derided. I was envious, never dreaming that thanks to John Dobson, much larger reflectors could be made portable.

The combination of Mike Lockwood's great fast mirrors and your fabulous telescopes has been revolutionary. it took courage on both your parts to do this. Innovation isn't easy though it can be fun.

Credit must also go to Al Nagler, whose Paracorrs made short Dobs feasible. In some sense a Paracorr-equipped scope is a compound scope.

And in this instance, credit also to Bob Schilling for having the courage to try new things.

John, you and I and the prize-winning telescope maker Ross Sackett, and the late mirror maker and telescope maker Dick Wessling, constitute a small band of devotees of integral wheels.

I am glad to see that Bob Schilling has joined us in this enthusiasm. I have found it hard to convince people of the merits of integral wheels, but I am greatly enjoying them on the Sweet Sixteen; just tilt and roll.

Looking at the photo of the 25" on your web site I realized for the first time that integral wheels and the wheelbarrow system can easily be used on the same scope, one for tilting and rolling in and out of a garage, and one for wheeling up ramps into a van.

Once again, thanks for a beautiful scope, so easy to use. The views of the summer objects at Stonelick State Park last weekend were glorious.

Best regards,
Bill


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: auriga]
      #5977456 - 07/18/13 08:57 AM

Bill, I have assuredly joins the ranks of believers that integral wheels on a telescope make all the difference in terms of easy deployment. John Pratte very cleverly devised a system on my 20" where there are two sliding bolts on the rear, an articulating turnbuckle on the front of the scope to lock in the altitude movements and a drop in bolt that stabilizes azimuth movement. This all works in concert to just tip the scope over after grabbing the UTA and rolling it out to its observing position.

The extra cleverness employed by John was that the wheels can also be mounted on the axles of a pair of wheelbarrow handles that John crafted to roll the scope up a ramp as you had mentioned.

As recently as last night, I wanted to get some quick looks at Saturn. I rolled out my 20" f/3 Lockwood/JP Astrocraft and also rolled out my AP130 EDT that is mounted on a rolling G11 tripod with a DM-6 alt/az head attached. The views of Saturn were exquisite with the AP130 but there was so much more detail available with the 20" Newt where a higher number of Saturnian moons were observed.

I am so hooked on the ease of rolling equipment that my AP900 mount that is used with my 6" Lunt solar scope is also on wheels so I never have to lift a thing.

When you get scopes that are designed for ease of use, they simply seem to get more use At least, that is what I have experienced.

In terms of John using the Comprehensive Boundary Layer Mitigation System (CBLMS), I ALWAYS observe with the 20" with both the blowing front fan onto the primary and rear sucking fan with its annulus around the primary and enclosed back of the mirror box to scrub the boundary layer off of the primary. As John has found, the benefits in steadier temperature conditions seem to be less but they always seem to be better than not having both sets of fans running at the same time in any conditions. As John stated, the variables of front and rear fan speeds are still an unfolding story for him as well as myself.

Bob


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #6105060 - 09/27/13 10:40 PM

Astro Buds, It has been a really rainy summer in North Florida. However, there is a dry mass of air coming in overhead and I got out the trusty 20" f/3 JP Astrocraft tonight. I was initially looking up with a Leica ASPH 8.9-17.8mm zoom that I used with the scope at 5:30 a.m. Eastern to look at Jupiter and the Moon early this morning. The seeing was so-so this morning. It is a little better tonight but not spectacular. Since I have a Mallincam Hyper astrovideo camera with focal reducer resident in the scope's holster and a 3.5" color LCD Watec monitor also permanently mounted on the scope, I decided that it was time to see some old friends in living color. The Mallincam turns my 20" f/3 into something like a 100-150" telescope in terms of what can be seen in detail and color. The "Pillars of Creation" (M16 - Eagle Nebula) were spectacular at 14-28 second integrations of the camera. More than that and the image was blown out because I am effectively operating the scope at about f/1.8 which really reduces the need for long exposures.

M17, M20 and M8 were all beautiful! I especially like seeing both the pinkinsh/red emission portion of the Trifid and the striking blue portion of the reflection part of the nebula. M57 was pretty unimpressive with an eyepiece but the two central stars, the "ears" and the two stars in the ring with pinks, greens, and whites are beautiful with the internal zoom of the camera on.
The advantages I am experiencing with a scope that is designed for both visual and astrovideo with little pain in terms of setup really seem to be paying dividends tonight. This has been an interesting 15 hours today because I was fortunate enough to spend about 30 minutes mid-day with my Lunt 152 solar scope and the views showed a lot of activity on our closest star. Other than about 5 glorious days last New Moon period, it has been a tough Summer for clear skies here in North Florida. Glad that Fall is just around the corner with better skies to come. Bob Schilling

Edited by Bob S. (09/28/13 11:33 AM)


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Relativist
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #6105114 - 09/27/13 11:37 PM

That's awesome, do you plan on broadcasting on NSN?

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Bob S.
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Relativist]
      #6105122 - 09/27/13 11:43 PM

Quote:

That's awesome, do you plan on broadcasting on NSN?




Curtis, Probably not at this time. It would seem to add a bit too much overhead to my workload. However, I have a laptop computer integrated into the telescope that resides in the computer/Argo/control hood that will talk with both my Mallincam Xtreme that I have as well as the Argo Navis/Servocat system through Sky X. As you can imagine, for me, all of these "dodads" seem a bit daunting and I am going to have to work my way into seamlessly using all of the components and then adding broadcasting. Seems very doable and I suspect in this coming year it will happen even though I am getting a bit long in the tooth to be trying to integrate so many activities into a session


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #6106044 - 09/28/13 02:08 PM

I suggest if your wanted to broadcast you could get help from the experienced people over on the VEAA forum and on NSN. I am working on getting set up to broadcast as well, but my motivation is low as I have access to only a sliver of sky from my balcony at home. It sound like your very close to having all the elements there, since the main difference would be that instead of sending the mallincam output only to the monitor you would also send it through a video converter into the computer.

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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Relativist]
      #6242212 - 12/09/13 09:07 AM

Well, the saga of the 20" f/3 1.25" thick Lockwood/JPA continues. I brought it to my darker site this past month for different nights of viewing. As many of you will remember, I have maglev fans on potentiometers both blowing on the front boundary layer and a rear fan with an annulus around the primary sucking air out of the back of an enclosed mirror box. What is very interesting about these experiments is that the results remain equivocal. On some nights, the fan systems are additive, on other nights the rear fan can be subtractive in terms of the scope's performance. On one particular night with the primary equilibrated, turning on the rear fan while the front fan was not blowing on the primary caused a noticeable darkening of background contrast while looking at the double cluster in Perseus. On other nights, the effect was not noticed.

Another astro-bud and I surmised that the reason that there is so much controversy about fan use in open tube Newtonians is that there appear to be a lot of variables that must be interacting to make the fan systems sometimes additive, sometimes neutral and sometimes subtractive in the performance of the telescope. I hope at some time to figure out what these variables may be but for the time being, I just have to experiment each night to ascertain what works best for the particular circumstances I am dealing with on a given night. The bottom line is that I am very glad that I have these fans systems in place and generally find that at least the front fan that is hidden in the shadow of the secondary gently blowing away the surface boundary layer seems to be consistently additive or at worst neutral in the performance of the fast Newtonian. Bob


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Cotts
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #6242435 - 12/09/13 11:22 AM

I am inspired by this thread to look into installing a suspended front fan in my 16" Teeter/Zambuto. The even cooling of my mirror is a big issue here in the Great Lakes area on most evenings. The Teeter design has a small fan blowing on the back of the mirror but it is not variable rate. I think I could turn it around to 'suck' air from the back while the new front fan blows on the front. (would simply reversing the wiring reverse the fan?) The trick for me will be to find a fan small enough to 'hide' in the shadow of my 3.1" secondary mirror....

This will be a nice winter project....

Dave


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Pinbout
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Cotts]
      #6242445 - 12/09/13 11:29 AM

do you think this will be small enough

http://www.mpja.com/12VDC-1-3_16-Square-X-3_4-Box-Fan-Eina/productinfo/30321%...


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Cotts
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Pinbout]
      #6242559 - 12/09/13 12:31 PM

Danny, that's a tiny one for sure, maybe too tiny. My diagonal is 3.1" diameter so a fan with a housing diagonal of 3" or less would do... A bit of trig gives 3.00"/1.414 = 2.12" maximum side length for a square housing.

I've just been looking for the MagLev fans which are virtually zero vibration.

Do you know of a source?

Dave


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mark cowan
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Cotts]
      #6242793 - 12/09/13 02:37 PM

There are easily available low noise fans for computer cooling that use magnetic suspension bearings - but they're not called "maglev". Off hand no I don't know which they are.

Best,
Mark


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Cotts
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: mark cowan]
      #6242941 - 12/09/13 03:41 PM

Here are the maglev fans. clicky thingy

I have found distributers here in Canada for these. "Maglev" is a brand name, though, from SUNON,, a Chinese manufacturer.

Dave


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: audioaficionado]
      #6245348 - 12/10/13 05:46 PM

I agree, at the Deep South Regional Stargaze I was reminded of that climbing an aluminum ladder to peer through a 25-inch F/4 truss-tube Dob. This and the fact there is no way I could keep a bigger telescope in the house and still get it through the door was why I opted to build my 15-inch F/4.5. It's still a work in progress, I am upgrading the secondary mirror from a 2.6" to a 3.1" minor axis diagonal to get better edge illumination with my low power eyepieces. The eyepiece height is perfect, no ladders needed and I like sitting in a chair while looking through it. I can only imagine just how much better the views would be through that 20-inch F/3......

Taras


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astrocrafter
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Achernar]
      #6245478 - 12/10/13 06:43 PM

Dave,
if you want to stay within the secondary shadow with the fan it has to be smaller than your 2.12" as the shadow of the secondary is converging after reflection.
John


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GeneT
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #6245764 - 12/10/13 08:53 PM

I am not jealous, I am not jealous, I am not jealous. . . .

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Cotts
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: astrocrafter]
      #6245914 - 12/10/13 10:10 PM

Quote:

Dave,
if you want to stay within the secondary shadow with the fan it has to be smaller than your 2.12" as the shadow of the secondary is converging after reflection.
John




The light cone converges after reflection from the primary, that's for sure, and continues to converge after hitting the secondary and exits the tube sideways.. The 3.1 "secondary 'eclipses' the incoming light which is arriving parallel to the scope axis. There is no convergence of this shadow. It is the shadow that we see when the scope is out of focus. You can hide anything you like behind this shadow as it contains no light.

Dave


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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Cotts]
      #6246429 - 12/11/13 07:04 AM

You guys are making me think before my coffee, but I have to agree with John.

"There is no convergence of this shadow."

That's right, but we don't want to observe the details of the shadow, it's the sky we are interested in. The marginal rays that graze the edge of the secondary on the way in converge after reflection from the primary on the way back up to the secondary, so you need a smaller fan to avoid blocking the smaller circle of converged marginal rays.


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Cotts
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Howie Glatter]
      #6247295 - 12/11/13 03:23 PM

OK, Howie. Coffee or no you make a good point and I will stand corrected. However, if the fan is suspended about 3" above the primary mirror, how much convergence will have occurred in that small a distance? I'm going to get my crayons and slide rule out to figure this out...

Stay tuned.

Also, it occurs to me, what are the chances I could have gotten a fan that was exactly 2.12" on a side anyway? I probably will get the fan closest to the 2.12" figure without going over - a 'Price is Right' solution... The fan might be 1.9" or 1.8" or.....?

Dave


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Cotts
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Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Cotts]
      #6247338 - 12/11/13 03:46 PM

OK. So my 3.1" secondary's shadow on the mirror is 3.1" in diameter. This converges to the focal point 80" away. (my scope is f/5) Thus we have an isosceles triangle with a base 3.1" and a height of 80".

To make the math easier we'll cut the base in half to make a right triangle.

So we now have a right triangle with a base of 1.55" and a height of 80". If the fan is 3" above the mirror we have a similar right triangle of 77" height and unknown base. By proportionality we find the unknown base to be 1.492". Thus the mirror's shadow is now 2.984" diameter circle at 3" above the primary mirror.

So the converged secondary's shadow is 2.984" wide 3" above the primary mirror. Thus the maximum square dimension that fits in that circular shadow is 2.984/1.414 = (drum roll) 2.11".

0.01" from my calculation before...

I do see that if there is a steeper light cone in an f/4 or f/3 scope and/or if the fan is mounted quite high above the primary mirror the calculations above would yield a much more significant difference..

And my chances of finding a fan exactly 2.11" on a side remain very small indeed..

Dave


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Bob S.
Carpal Tunnel
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Reged: 07/14/05

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Cotts]
      #6247346 - 12/11/13 03:49 PM

Dave,

FYI, my front blowing Maglev fan is about 8" above my 20" f/3 primary. The scope is at another location at present so I cannot get you a measurement of the size of the fan. I would be a bit concerned about getting the fan too close as it might create unwanted turbulence. I like my fan gently blowing toward the primary lightly disrupting the boundary layer. I have not done a smoke test to get a sense of how much the air is moved with the fan at its lowest speed setting.

Bob


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Cotts
Just Wondering
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Reged: 10/10/05

Loc: Toronto, Ontario
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #6247369 - 12/11/13 03:59 PM

Hi, Bob. I just pulled that 3" figure out of my ear. I went to the scope and the more realistic number is also 8" for my scope too. I'll be attaching the fan wires to a circular baffle inside the mirror box which sits about 8" up.

So, I crunch the numbers again as above and my fan now can be no larger than 1.97" on a side......

And, Bob, while I have your ear, would guitar strings be suitable for suspending the fan? Guitar machine heads could be used to tighten the wires, too. Maybe?

Dave


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astrocrafter
Vendor (JP Astrocraft)


Reged: 11/24/10

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Cotts]
      #6247405 - 12/11/13 04:17 PM

Hi Dave,
I used the guitar heads on my 25" with guitar strings.
The little brass donuts on the anchor end were perfect to solder the fan power wires to as the strings carry the current. I was never sure what pitch to tune them to though.
John


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mark cowan
Vendor (Veritas Optics)
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Reged: 06/03/05

Loc: salem, OR
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Cotts]
      #6247406 - 12/11/13 04:17 PM

Quote:

And my chances of finding a fan exactly 2.11" on a side remain very small indeed..




But 50mm frame size fans are very easy to find... Which is almost exactly 1.97".

Best,
Mark


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Cotts
Just Wondering
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Reged: 10/10/05

Loc: Toronto, Ontario
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: mark cowan]
      #6247488 - 12/11/13 05:04 PM

Mark, John and Bob, you guys make me believe this project will work in a 16" scope. And so, I will amass the goodies and install it all....

I'll start my own thread with this project...

One last question. I'll have to reverse the fan behind my mirror so that it 'sucks' from the mirror rather than blowing on the back of the mirror as it now does. Will changing the polarity of the wiring accomplish this? Or must I physically remove and re-install the fan pointing the other way?

thanks,

Dave

Edited by Cotts (12/11/13 05:09 PM)


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Bob S.
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Reged: 07/14/05

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Cotts]
      #6247534 - 12/11/13 05:31 PM

Quote:

Mark, John and Bob, you guys make me believe this project will work in a 16" scope. And so, I will amass the goodies and install it all....

I'll start my own thread with this project...

One last question. I'll have to reverse the fan behind my mirror so that it 'sucks' from the mirror rather than blowing on the back of the mirror as it now does. Will changing the polarity of the wiring accomplish this? Or must I physically remove and re-install the fan pointing the other way?

thanks,

Dave




Dave, I am not able to address the polarity part of the question. In discussions with John Pratte, it would be VERY interesting to have the rear fan capable of blowing onto the back of the mirror and/or be able to flip it over and have the air sucking out of the rear of the mirror box. The reason that John and I are interested in the possibility of reversing the rear fan is that there is potential to change the figure of the mirror and possibly go from being undercorrected to overcorrected if you only cool the edges of the primary with the sucking fan running after or even before the primary mirror has equilibrated. If you could devise a way to be able to flip the fan at will without a lot of trouble, this would allow you to ascertain which direction, the rear fan blowing or sucking is most efficacious. If it is possible for you to put this into your build plans, I think you will help to answer for yourself and some of us others as to what seems to be working best. On Joe Wambo's 32" scope, he has a front fan blowing on the primary and a rear fan blowing on the back of the mirror and is getting pretty superb results. Bob


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Starman1
Vendor (EyepiecesEtc.com)
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Reged: 06/24/03

Loc: Los Angeles
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Cotts]
      #6247556 - 12/11/13 05:45 PM

Quote:

OK. So my 3.1" secondary's shadow on the mirror is 3.1" in diameter. This converges to the focal point 80" away. (my scope is f/5) Thus we have an isosceles triangle with a base 3.1" and a height of 80".

To make the math easier we'll cut the base in half to make a right triangle.

So we now have a right triangle with a base of 1.55" and a height of 80". If the fan is 3" above the mirror we have a similar right triangle of 77" height and unknown base. By proportionality we find the unknown base to be 1.492". Thus the mirror's shadow is now 2.984" diameter circle at 3" above the primary mirror.

So the converged secondary's shadow is 2.984" wide 3" above the primary mirror. Thus the maximum square dimension that fits in that circular shadow is 2.984/1.414 = (drum roll) 2.11".

0.01" from my calculation before...

I do see that if there is a steeper light cone in an f/4 or f/3 scope and/or if the fan is mounted quite high above the primary mirror the calculations above would yield a much more significant difference..

And my chances of finding a fan exactly 2.11" on a side remain very small indeed..

Dave



The shadow is 3.1" only for the axial ray. Off-axis rays come in at different angles and move the shadow back and forth.
The shadow of the secondary, like the shadow of the Earth, has an umbra and a penumbra. The umbra's size depends on the size of the maximum true field of the instrument, as does the penumbra.
A back-of-the-envelope calculation shows the penumbra is actually larger than the secondary, while the umbra is smaller. For every point in the field, the shadow is 3.1" in diameter, it's just that the position of that 3.1" shadow on the primary shifts according to where that point in the field is.
At any rate, the umbra is not a lot smaller than the secondary (you could use simple trigonometry to figure out its size), as you've obviously figured out.


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Mirzam
Post Laureate
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Reged: 04/01/08

Loc: Lovettsville, VA
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft new [Re: Bob S.]
      #6248476 - 12/12/13 08:27 AM

I've used velcro to hold my mirror fans to the mounting surface. Then you can easily flip them around to reverse direction. Oddly enough, the fans I have tried do not reverse direction when the polarity is reversed. They simply do not turn.

After experimentation with closed tube scopes I always blow air up the tube. It seems to work better in these cases, but of course an open tube may behave differently.

JimC


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