Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

Equipment Discussions >> Reflectors

Pages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | (show all)
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.]
      #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.


Post Extras: Print Post   Remind Me!   Notify Moderator  
cpr1
professor emeritus
*****

Reged: 03/24/12

Loc: Louisiana
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.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

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)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

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)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

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)


Post Extras: Print Post   Remind Me!   Notify Moderator  
astrocrafter
Vendor (JP Astrocraft)


Reged: 11/24/10

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


Post Extras: Print Post   Remind Me!   Notify Moderator  
Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

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


Post Extras: Print Post   Remind Me!   Notify Moderator  
astrocrafter
Vendor (JP Astrocraft)


Reged: 11/24/10

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


Post Extras: Print Post   Remind Me!   Notify Moderator  
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: 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.


Post Extras: Print Post   Remind Me!   Notify Moderator  
jim molinari
member
*****

Reged: 02/02/08

Loc: California
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


Post Extras: Print Post   Remind Me!   Notify Moderator  
SkyRanger
super member
*****

Reged: 10/21/10

Loc: Prescott Valley, AZ
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


Post Extras: Print Post   Remind Me!   Notify Moderator  
Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

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


Post Extras: Print Post   Remind Me!   Notify Moderator  
johnnyha
Postmaster
*****

Reged: 11/12/06

Loc: Sherman Oaks, CA
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.

Post Extras: Print Post   Remind Me!   Notify Moderator  
BrendanF
super member


Reged: 12/04/07

Loc: Los Angeles, CA
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?


Post Extras: Print Post   Remind Me!   Notify Moderator  
Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

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


Post Extras: Print Post   Remind Me!   Notify Moderator  
BrendanF
super member


Reged: 12/04/07

Loc: Los Angeles, CA
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


Post Extras: Print Post   Remind Me!   Notify Moderator  
Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

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)


Post Extras: Print Post   Remind Me!   Notify Moderator  
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.]
      #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!


Post Extras: Print Post   Remind Me!   Notify Moderator  
turtle86
Pooh-Bah Everywhere Else
*****

Reged: 10/09/06

Re: First Light On My 20" f/3 Lockwood/JP Astrocraft [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.


Post Extras: Print Post   Remind Me!   Notify Moderator  
johnnyha
Postmaster
*****

Reged: 11/12/06

Loc: Sherman Oaks, CA
Re: First Light On My 20" f/3 Lockwood/JP Astrocraft [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.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | (show all)


Extra information
19 registered and 33 anonymous users are browsing this forum.

Moderator:  ausastronomer, Phillip Creed, JayinUT, okieav8r 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 18681

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics