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Equipment Discussions >> Reflectors

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Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft [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
Vendor (JP Astrocraft)


Reged: 11/24/10

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
Vendor (JP Astrocraft)


Reged: 11/24/10

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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auriga
Pooh-Bah


Reged: 03/02/06

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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Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

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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Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

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
Post Laureate
*****

Reged: 10/11/03

Loc: OC, CA, USA
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.
Carpal Tunnel
*****

Reged: 07/14/05

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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Relativist
Post Laureate
*****

Reged: 10/11/03

Loc: OC, CA, USA
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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Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

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
Just Wondering
*****

Reged: 10/10/05

Loc: Toronto, Ontario
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
Postmaster
*****

Reged: 02/22/10

Loc: nj
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
Just Wondering
*****

Reged: 10/10/05

Loc: Toronto, Ontario
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
Vendor (Veritas Optics)
*****

Reged: 06/03/05

Loc: salem, OR
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
Just Wondering
*****

Reged: 10/10/05

Loc: Toronto, Ontario
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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Achernar
Postmaster
*****

Reged: 02/25/06

Loc: Mobile, Alabama, USA
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
Vendor (JP Astrocraft)


Reged: 11/24/10

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
Ely Kid
*****

Reged: 11/07/08

Loc: South Texas
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
Just Wondering
*****

Reged: 10/10/05

Loc: Toronto, Ontario
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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Howie Glatter
Vendor


Reged: 07/04/06

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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