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 >> Cats & Casses

Pages: 1 | 2 | 3 | 4 | (show all)
pfile
Post Laureate


Reged: 06/14/09

Re: AT6RC collimation under different loads new [Re: pfile]
      #5516721 - 11/12/12 08:51 PM Attachment (30 downloads)

well, this is interesting: on the AT6, when i attach the tak collimation scope, the donut on the secondary is definitely not centered up. furthermore if i rotate the focuser, the light area around the dot moves as i rotate the focuser, as though it's orbiting a point.

i *think* this means that the focuser first needs collimation/tilt adjustment as per John D's instructions above. then perhaps the scope needs collimation.

strange as CCDInspector says everything's mostly okay with the reducer/flattener in place. can an FR/FF really cover up a collimation problem?


Post Extras: Print Post   Remind Me!   Notify Moderator  
pfile
Post Laureate


Reged: 06/14/09

Re: AT6RC collimation under different loads new [Re: pfile]
      #5517184 - 11/13/12 01:39 AM

well i fixed up the AT6 but then did not test it, since the AT10 is on the G11 right now. i messed with the AT6 primary, which perhaps i should not have done. when i got the outer annulus of the primary to be concentric, the shadow of the baffle was way off... so i put it back.

i put the tak scope on the AT10 and it looked mostly okay, but i tried to center up everything a little better just by adjusting the secondary a tad.

whaddya know? round stars with no coma. CCDInspector says it's off by 3" now. seems like i can tweak it a little more but i was worried that i'd mess it up.

i think the seeing is not that good tonight as even though my B-mask says focus is spot on, the stars look a little fat.

i'm not sure i'm out of the woods yet, but thanks to everyone for their insights and ideas. i probably will upgrade the focuser and then i'll have to go thru this all again...


Post Extras: Print Post   Remind Me!   Notify Moderator  
jaddbd
professor emeritus


Reged: 05/18/05

Loc: Woodbine, MD
Re: AT6RC collimation under different loads new [Re: pfile]
      #5518971 - 11/14/12 12:58 AM

Quote:

well, this is interesting: on the AT6, when i attach the tak collimation scope, the donut on the secondary is definitely not centered up. furthermore if i rotate the focuser, the light area around the dot moves as i rotate the focuser, as though it's orbiting a point.

i *think* this means that the focuser first needs collimation/tilt adjustment as per John D's instructions above. then perhaps the scope needs collimation.

strange as CCDInspector says everything's mostly okay with the reducer/flattener in place. can an FR/FF really cover up a collimation problem?




If you do get a adjustable focus ring, I think Jared's suggestion of leaving the focuser put is a good one. I actually went the the trouble of getting the laser to agree with the centered chesire view and a good star test -i.e. with donut centered in the chesire and a good star test, I can spin the focuser with the laser and the it remains pointed at the center spot. It took me forever to get it there thru much trial and error (I can't even give you a good way to do it) and there is really no need to be able to spin the focuser. Also, bear in mind that you may loose the a slight bit of symmetry on the outer ring looking thru a chesire if you tilt the focuser since you may end up slightly out of parellel with the baffle tube. I assume the tak scope does not see these anyway... (I use a "poor mans tak scope," small set of binocs thru a tecton chesire.)

FYI, I took a purely mechanical approach to my collimation due to my chip size (ST2000 is about 2/3 the FOV of your chip). There is hardly any dicernible coma "doppler effect" in the corners of my images in focus unless the collimation is out of wack. I can detect the "fleeing astig" in the corners of defocused images however. I don't need a field flattner with my camera.

Good luck,

JD


Post Extras: Print Post   Remind Me!   Notify Moderator  
pfile
Post Laureate


Reged: 06/14/09

Re: AT6RC collimation under different loads new [Re: jaddbd]
      #5519352 - 11/14/12 11:01 AM

you can actually see all the rings in the tak scope, including the outer edge of the mirror. what's weird is that on the 6 i cant simultaneously get the baffles centered up on the secondary and also see the entire outer edge of the primary.

supposedly the moonlites are collimated at the factory, and i have not messed with the focuser tilt, so i'm not sure why i'd be off axis like that. maybe the scope is mechanically messed up.

yeah - i don't have any intention of rotating the focuser, i'm going to leave it put.


Post Extras: Print Post   Remind Me!   Notify Moderator  
pfile
Post Laureate


Reged: 06/14/09

Re: AT6RC collimation under different loads new [Re: pfile]
      #5521227 - 11/15/12 01:25 PM

random updates: on the AT6RC, the reason i could not get the image of the primary mirror centered up is that the Tak scope was crooked (!!). it has a very deep groove and unless the focuser's brass ring is down in this groove, the scope will be crooked. the scope's flange ends up not flush with the focuser when it's installed properly.

on the AT10RC, i tried CCDInspector's defocused star collimation tool (using Altair) and ended up worse off than what i had with the Tak. that's kind of disappointing. but what's interesting is my original star shapes were kind of triangular/boomerang shaped. i think the secondary mirror must have been pinched somehow since no matter how far off the collimation is now, i never see star shapes like that. maybe just loosening/tightening one of the secondary collimation screws relieved the pressure.

looks like 2 weeks of clouds and rain now, so testing is probably over. what's bothering me about the AT10 is that no matter how close i've been to proper secondary alignment, i've never seen a FWHM less than about 4 at the optical center. it could be that it would dramatically improve once collimation is spot on...?


Post Extras: Print Post   Remind Me!   Notify Moderator  
JoseBorrero
Post Laureate
*****

Reged: 09/04/09

Loc: Puerto Rico Island
Re: AT6RC collimation under different loads new [Re: pfile]
      #5522963 - 11/16/12 01:57 PM

best collimator is the chessire eyepiece from scopestuff. http://www.scopestuff.com/ss_ec13.htm I used for my AT6RC with no problem, follow the instruction in the scope manual.


consider a Moonlite focuser as it has more torque.


Post Extras: Print Post   Remind Me!   Notify Moderator  
pfile
Post Laureate


Reged: 06/14/09

Re: AT6RC collimation under different loads new [Re: JoseBorrero]
      #5522971 - 11/16/12 02:04 PM

the tak scope is much the same and is also good for collimating RC telescopes. i do already have a moonlite focuser on the AT6RC. this is why i was surprised that it was apparently sagging. but i don't think it is sagging.

at this point i believe the AT6RC is collimated properly, but i have not been able to do the star test due to the weather.


Post Extras: Print Post   Remind Me!   Notify Moderator  
jaddbd
professor emeritus


Reged: 05/18/05

Loc: Woodbine, MD
Re: AT6RC collimation under different loads new [Re: pfile]
      #5523424 - 11/16/12 08:23 PM Attachment (27 downloads)

I downloaded a copy of ccdinspector to see how the collimation matched. I am feeling better about my methods. Cool program. I put about a 30th of screw turn to get the collimation error from hovering around 3" to get it to hover around 1". Seeing is less than average tonight.

I have not seen the AT6, but I still think the whole primary assembly might not be slipping. You problably already have, but I would make sure the primary lock screws are tight, and the small primary collimation screws are at least firm to the allen wrench... also check the screws that hold the rear plate to the tube (on the side of the tube).

John D


Post Extras: Print Post   Remind Me!   Notify Moderator  
pfile
Post Laureate


Reged: 06/14/09

Re: AT6RC collimation under different loads new [Re: jaddbd]
      #5523561 - 11/16/12 10:30 PM

that curvature map looks great. nice work.

good point about the side screws. i'll check those. i had to remove/replace the top 2 screws to mount a vixen rail on top, but i had done that long before i tried the STT-8300.

of course now i have adjusted the primary in the AT6 so yeah, before i take it outside again i'll make sure the collimation lock screws are tight. now i'm not certain that the secondary was so far out of whack due to my problem aligning the tak scope, but at this point that's all behind me - the mirrors have been moved!

on the AT10 the secondary collimation screws are pretty tight - i'm not sure i could move them 1/30th of a turn! but i can see that such tiny adjustments are needed once you get close.


Post Extras: Print Post   Remind Me!   Notify Moderator  
jaddbd
professor emeritus


Reged: 05/18/05

Loc: Woodbine, MD
Re: AT6RC collimation under different loads new [Re: pfile]
      #5523651 - 11/16/12 11:34 PM

Quote:

that curvature map looks great. nice work.

good point about the side screws. i'll check those. i had to remove/replace the top 2 screws to mount a vixen rail on top, but i had done that long before i tried the STT-8300.

of course now i have adjusted the primary in the AT6 so yeah, before i take it outside again i'll make sure the collimation lock screws are tight. now i'm not certain that the secondary was so far out of whack due to my problem aligning the tak scope, but at this point that's all behind me - the mirrors have been moved!

on the AT10 the secondary collimation screws are pretty tight - i'm not sure i could move them 1/30th of a turn! but i can see that such tiny adjustments are needed once you get close.




If 6 has middle screws under the rails like the 10, they also hold the tube to the back plate.

Also, the secondary collimation screws push/pull against the center screw. So you can loosen all a bit 3 equa-distant to give them more play if they are to tight. 1/30 - think of 2 minutes on the clock - a tiny tweak...

Hope to hear good things about the STT - I have that on the radar right now...


Post Extras: Print Post   Remind Me!   Notify Moderator  
CCDMan
member


Reged: 03/10/10

Loc: Oregon, USA
Re: AT6RC collimation under different loads new [Re: pfile]
      #5718501 - 03/07/13 01:56 PM

I have owned two RCOS scopes and an OGS and have a AT10RCF on order (my 14.5 RCOS is too heavy for my bad back). I have to wonder what imbecile decided to mount the focuser the way AT did?! It really could not have saved that much money. Fortunately, I have a big lathe and if push comes to shove I plan to machine a completely new rear cell with the focuser mounted the way it should have been in the first place, on the back plate with the primary cell attached the back plate by the collimation screws. What the heck, just some aluminum and some time. The aluminum is cheap and my time as a retired guy is worth nothing at all!

Does anyone have pictures of how the rear cell is attached to the carbon tube? Not very good pics on the web. It appears that there are (3?) screws thru the carbon fiber that hold the rear cell to the tube. Hopefully they did not glue it as well. Looks like one would just disassemble, remove the primary, cut off the back of the tube where the focuser attaches now, and build a ring that attaches to the tube and a flat rear cell plate which the primary collimation mechanism and the focuser attach to. In other words how everyone BUT the Chinese do it! As long as you keep it close to centered (and that can be adjusted with the secondary anyway to a degree) and maintain the correct mirror spacing, you would wind up with a much better system.

An alternative method, and much simpler if the die cast rear cell is strong enough, would be to machine two large rings that would go both behind and in front of the back wall of the present die cast rear cell just around the light path opening. Then drill 3-4 symmetric holes, say 1/4-3/8 diameter and tap the inner ring to receive the bolts. The outer ring would sit out on standoffs just far enough out to clear the convex curvature of the backside of the rear cell. The focuser of choice could mount to the plate. The standoffs could be adjusted to make for a perfectly aligned focuser and any light gap could be sealed with a large o-ring.

Trust me, a properly made RC is not at all hard to collimate, I can do my RCOS 14.5 in about 15 minutes and nail it every time to the point where a star tweak is only needed about 20% of the time. The problem is that this thing does not seem to fit the definition of "properly made". So properly remake it. <g>

One thing I should point out is that you really do not want to use the Tak scope just in the focuser. The focuser should be off the scope. Use a machined, threaded adapter and some machined, threaded extension tubes that will put the Tak scope back where the focuser would be. The better RC scopes use 2.7 AP extension tubes threaded together, threaded into a plate machined to attach to the rear cell. That plus a custom AP to Tak scope adapter for the back end of the AP tubes. I have a AT10RC rear thread to AP thread adapter ordered from Precise Parts to get me there for this scope (did not feel like making one myself <g>). If you use the Tak just in your focuser, you are just introducing another variable that has to be sorted out. Note that you can still use the Tak scope on the back of the focuser and if the two methods do not agree, your focuser can be identified as at least part of the problem.

Edited by CCDMan (03/07/13 07:33 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
pfile
Post Laureate


Reged: 06/14/09

Re: AT6RC collimation under different loads new [Re: CCDMan]
      #5719539 - 03/07/13 10:29 PM

well that would be an awesome mod, that's for sure. i have been imaging with the at10rc and have not returned to the at6rc. it still needs to be star tested.

i don't have carbon tube ATRCs but i do believe the metal one are held together as you describe.

are you using the deep sky instruments method of collimating with the camera attached?

Edited by pfile (03/07/13 10:30 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
CCDMan
member


Reged: 03/10/10

Loc: Oregon, USA
Re: AT6RC collimation under different loads new [Re: pfile]
      #5720289 - 03/08/13 11:02 AM

Quote:

are you using the deep sky instruments method of collimating with the camera attached?




No, never. I have tried that and it is a major hassle. If done right, and I just did it pre-sale on my 14.5 RCOS last night, it is quicker and just as accurate with a good eyepiece (after doing daytime collimation with a laser and Tak scope). It does not entirely apply to the ATRC scopes but Ken Crawford did a great video on RC collimation that is on the RCOS site.

Having said that, I acquired sanity last night after thinking thru this purchase and plan to call Anacortes when they open and cancel the ATRC order and order a Tak TOA 130 instead. Shorter F.L but WAY easier to deal with. I am getting too old for this S***.....


Post Extras: Print Post   Remind Me!   Notify Moderator  
saadabbasi
Pooh-Bah


Reged: 08/23/09

Loc: 29N
Re: AT6RC collimation under different loads new [Re: CCDMan]
      #5720293 - 03/08/13 11:05 AM

Quote:

Quote:

are you using the deep sky instruments method of collimating with the camera attached?




No, never. I have tried that and it is a major hassle. If done right, and I just did it pre-sale on my 14.5 RCOS last night, it is quicker and just as accurate with a good eyepiece (after doing daytime collimation with a laser and Tak scope). It does not entirely apply to the ATRC scopes but Ken Crawford did a great video on RC collimation that is on the RCOS site.

Having said that, I acquired sanity last night after thinking thru this purchase and plan to call Anacortes when they open and cancel the ATRC order and order a Tak TOA 130 instead. Shorter F.L but WAY easier to deal with. I am getting too old for this S***.....




Good choice on the Tak. I find the collimation very difficult but then again I am rather inexperienced.


Post Extras: Print Post   Remind Me!   Notify Moderator  
pfile
Post Laureate


Reged: 06/14/09

Re: AT6RC collimation under different loads new [Re: CCDMan]
      #5721213 - 03/08/13 09:04 PM

Quote:


Having said that, I acquired sanity last night after thinking thru this purchase and plan to call Anacortes when they open and cancel the ATRC order and order a Tak TOA 130 instead. Shorter F.L but WAY easier to deal with. I am getting too old for this S***.....




i hear that... can't go wrong with takahashi.


Post Extras: Print Post   Remind Me!   Notify Moderator  
CCDMan
member


Reged: 03/10/10

Loc: Oregon, USA
Re: AT6RC collimation under different loads new [Re: pfile]
      #5750766 - 03/22/13 10:03 PM

UPDATE:

I indeed did get the TOA-130 but decided to also get the smaller AT8RCF. Dirt cheap after my credits at Anacortes
on the cameras and such so out of pocket was about 1,100. I figure for that price I can afford to play with a better
rear cell. It also helps that I picked up a used TOA-130 with 4 inch flattener for less than half retail for the new
one!

Will let the forum know how it goes and take pictures of any modifications. I will do this step-wise from standard
configuration, getting however radical is needed to deal with any issues. This will be fun. AT8 is due Monday, picked
up TOA today.


Post Extras: Print Post   Remind Me!   Notify Moderator  
pfile
Post Laureate


Reged: 06/14/09

Re: AT6RC collimation under different loads new [Re: CCDMan]
      #5751143 - 03/23/13 02:43 AM

excellent, yes, please keep us posted.

Post Extras: Print Post   Remind Me!   Notify Moderator  
CCDMan
member


Reged: 03/10/10

Loc: Oregon, USA
Re: AT6RC collimation under different loads new [Re: pfile]
      #5826368 - 04/27/13 01:46 PM

I have finally found time what with all the upgrades to my system (mainly refractors as they are my main "quality" scopes at this time) to begin messing with my "throw-away" AT8RC. I have not started testing yet but may begin as early as tonite.

I have made up a page where I will post my impressions and results as this proceeds. Since it must be combined with my real imaging on the refractors, it will be somewhat hit and miss and mainly done during full moon. Once I get to modifications (assuming they are required), I will also need to find the time to do the machining. The bottom line is this will be catch as catch can and may take much of the summer.

ATRC Testing and Modification

Take Care


Post Extras: Print Post   Remind Me!   Notify Moderator  
pfile
Post Laureate


Reged: 06/14/09

Re: AT6RC collimation under different loads new [Re: CCDMan]
      #5827413 - 04/27/13 10:20 PM

thanks i'll keep an eye on that page.

Post Extras: Print Post   Remind Me!   Notify Moderator  
frolinmod
Carpal Tunnel


Reged: 08/06/10

Loc: Southern California
Re: AT6RC collimation under different loads new [Re: CCDMan]
      #5827769 - 04/28/13 05:26 AM

According to your web page:

Quote:

Stay tuned to this page for testing results, updates, and modifications to the scope as they progress thru summer of 2103.




Gee, will it take you that long?


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | 4 | (show all)


Extra information
15 registered and 24 anonymous users are browsing this forum.

Moderator:  Cotts, Starman27, kkokkolis 

Print Thread

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


Thread views: 3639

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics