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My take on GSO Ritchey-Chrétien collimation

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#26 TinySpeck

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Posted 29 November 2020 - 07:12 PM

Definitely a concern I have. I've just lowered my expectations that I won't be able to collimate and have perfect mechanical alignment with the scope in all positions. The back focus on my RC6 scope is like 250mm. A scope engineered to experience zero flex over this great a distance would be much more expensive than the $400 I paid. smile.gif

 

I'm not sure what the experience has been of the OP as his scope is the RC8. 

That's the right attitude, celegroz.  This was my experience too (see OP paragraph 3).  The weight of the optical train will cause a tiny flex, and the amount will differ depending on where your scope is aimed.  In practice it makes little difference, and if you collimate at about 60 degrees altitude the error will be minimized for most imaging.  I'm waiting for an optical train which is hewn from a single block of quartz crystal for perfect rigidity.  grin.gif


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#27 celegroz

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Posted 29 November 2020 - 08:03 PM

Just a quick thought... check the laser spot while either rotating the laser in the focuser or with the laser in different rotational positions. My laser collimator is a tad out out of alignment and this procedure helps to null that out.

Yep. Did that and also checked to see if it was just slop of the 2 inch Farpoint laser in the compression ring. It's definitely way out of collimation. 



#28 celegroz

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Posted 29 November 2020 - 08:06 PM

  I'm waiting for an optical train which is hewn from a single block of quartz crystal for perfect rigidity.  grin.gif

Lol, it does make me wonder if there's a way to improve this by using an oversized dovetail plate as an earlier commenter mentioned. I have a friend in the machine shop business. Wondering if he could fabricate this with bracket that would bolt to the underside of the focuser to help support the load.



#29 TinySpeck

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Posted 29 November 2020 - 09:29 PM

Lol, it does make me wonder if there's a way to improve this by using an oversized dovetail plate as an earlier commenter mentioned. I have a friend in the machine shop business. Wondering if he could fabricate this with bracket that would bolt to the underside of the focuser to help support the load.

I think that could reduce it.  You'd have to work out a rigid method to attach it to your camera.  There will be temperature induced flexure too, though, regardless.  The limiting factor is the 2 arc-s or so of blur that comes from the atmosphere.  If you can keep your mechanical errors below that I think you're doing the best you can.

 

Yep. Did that and also checked to see if it was just slop of the 2 inch Farpoint laser in the compression ring. It's definitely way out of collimation. 

Yeah, compression rings are the bane of rigid optics.  I used a self-centering ring with my 1.25" Cheshire to try to keep it locked in the proper position.  If you can use screw threads as much as possible that would help.



#30 celegroz

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Posted 29 November 2020 - 10:36 PM

 If you can use screw threads as much as possible that would help.

Is there an effective way to attach the M42 threads on my 2600MC-pro to the 2" Moonlight other than a nose piece/compression ring? I researched this for a long while today and came up with nothing.

 

EDIT: Well, it looks like maybe I bought the wrong focuser. The 2.5 inch moonlight has 68mm threads on the focus drawtube. Could've attached a Baader quick-lock to that for a rock solid connection all the way. $445 for the 2.5 Moonlite though - ouch! 


Edited by celegroz, 29 November 2020 - 11:12 PM.


#31 TinySpeck

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Posted 30 November 2020 - 12:40 PM

Is there an effective way to attach the M42 threads on my 2600MC-pro to the 2" Moonlight other than a nose piece/compression ring? I researched this for a long while today and came up with nothing.

That's the only compression fitting I have in my train too.  I guess you need to have one rotateable fitting in there to get the orientation you want, and the Moonlite is a pretty good option for that.



#32 celegroz

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Posted 02 December 2020 - 02:42 PM

A bit of progress but still not there. Was able to fiddle with collimation using Farpoint laser and Cheshire. I believe I improved things but my stars are still not pinpoints. Collimation for the factory was WAY off. The other thing that concerns me is the focal length. Plate solving claims my focal length is 1392mm and the scope is spec'd for 1370mm. Should this be of concern? Do I need to address this before continuing with collimation? Here are the areas where I feel I'm struggling on the RC6:

 

1. Difficulty determining which way to turn the adjustment screws to center the laser in the secondary donut during focus tube collimation. I really struggled with this. Also, the Farpoint doesn't seem to make a nice, crisp dot so it's difficult to tell if I'm perfect. 

 

2. REALLY difficult to see if my secondary adjustments are reflecting the laser exactly back on itself. Used binoculars as you suggest but still I feel like I'm guessing. 

 

3. With a Moonlite focuser (non-motorized), extension tubes, focus tilt plate, and ASI2600MC-pro on the back, this little telescope is back-heavy! I can't balance it in the dec axis. I'll need to figure out how to add some weight to the front to address this. 


Edited by celegroz, 02 December 2020 - 02:50 PM.


#33 TinySpeck

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Posted 02 December 2020 - 03:05 PM

A bit of progress but still not there. Was able to fiddle with collimation using Farpoint laser and Cheshire. I believe I improved things but my stars are still not pinpoints. Collimation for the factory was WAY off. The other thing that concerns me is the focal length. Plate solving claims my focal length is 1392mm and the scope is spec'd for 1370mm. Should this be of concern? Do I need to address this before continuing with collimation? Here are the areas where I feel I'm struggling on the RC6:

 

1. Difficulty determining which way to turn the adjustment screws to center the laser in the secondary donut during focus tube collimation. I really struggled with this. Also, the Farpoint doesn't seem to make a nice, crisp dot so it's difficult to tell if I'm perfect. 

 

2. REALLY difficult to see if my secondary adjustments are reflecting the laser exactly back on itself. Used binoculars as you suggest but still I feel like I'm guessing. 

 

3. With a Moonlite focuser (non-motorized), extension tubes, focus tilt plate, and ASI2600MC-pro on the back, this little telescope is back-heavy! I can't balance it in the dec axis. I'll need to figure out how to add some weight to the front to address this. 

It sounds like your focal length is far enough off that it should be adjusted.  I wouldn't worry about a few mm, but you've got an error of 22 mm there.  (But confirm the spec'd focal length if you can.  The spec for my scope was wrong almost everywhere.)

 

The Glatter isn't a perfect dot either, but maybe the Farpoint is a bit worse.  It's only 1/3 the price, after all.  If it's at least circular and concentric you can work with it.  You might be able to add a circular aperture to the laser, if you can machine a nice concentric one.  I found that cleaned up my Glatter nicely.  It dimmed it a bit, but that was okay.

 

Does the Farpoint have a white front surface?  That makes it easier to see the laser image reflected back on it.  You can add your own paper donut if you want, but carefully center the hole in the paper on the laser opening.  I found it took a little staring to get comfortable with centering the spread-out laser image on the laser.  Follow one of the outer rings around with your eyes and look for symmetry.  Look for how well the diffraction rings line up on the white front donut.

 

Yeah, sounds like you'll need to put a few fishing weights on the front end of the OTA.  Hope you've got a good sturdy mount!



#34 celegroz

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Posted 02 December 2020 - 03:42 PM

It sounds like your focal length is far enough off that it should be adjusted.  I wouldn't worry about a few mm, but you've got an error of 22 mm there.  (But confirm the spec'd focal length if you can.  The spec for my scope was wrong almost everywhere.)

 

Ok. Not sure how I can determine this other than google'ing. 

 

 

Does the Farpoint have a white front surface?  That makes it easier to see the laser image reflected back on it.  You can add your own paper donut if you want, but carefully center the hole in the paper on the laser opening.  I found it took a little staring to get comfortable with centering the spread-out laser image on the laser.  Follow one of the outer rings around with your eyes and look for symmetry.  Look for how well the diffraction rings line up on the white front donut.

 

No. Attaching a picture. From a color perspective, it couldn't be much worse - black and red. LOL. I'll get these "whitened" as soon as possible. Great feedback! Thanks. 

FP laser

Edited by celegroz, 02 December 2020 - 04:44 PM.


#35 TinySpeck

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Posted 02 December 2020 - 04:32 PM

Ok. Not sure how I can determine this other than google'ing. 

 

 

No. Attaching a picture. From a color perspective, it couldn't be much worse - black and red. LOL. I'd get these "whitened" as soon as possible. Great feedback! Thanks. 

Yeah, that's about the worst possible reflective surface!  No wonder it's giving you trouble.  Well, cut yourself some nice circular donuts of white vinyl or paper and carefully center them on both the black and red surfaces if you can.  The red surface would be most important, if the spread out spot extends that far, because it's easier to center the diffraction rings than the big central blob.

 

Yes,  Google up the focal length and look for discrepancies.  I don't know if the mfr would be responsive, but you could try them.  I also found that my back focus didn't match the spec'd 250 mm until my focal length was correct, so that's another data point for you.



#36 glend

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Posted 03 December 2020 - 03:27 PM

The New TS RC/CC illuminated collimation tool is a cost effective solution, and very easy to use. I bought one for my CC, highly recommended.

 

https://www.teleskop...Telescopes.html



#37 TinySpeck

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Posted 03 December 2020 - 04:10 PM

The New TS RC/CC illuminated collimation tool is a cost effective solution, and very easy to use. I bought one for my CC, highly recommended.

 

https://www.teleskop...Telescopes.html

That's an interesting and inexpensive alternative.  Reading the instructions, though, the procedure is to adjust the secondary tilt, then the primary, and you're done.  But adjusting the primary tilt on the GSO style RC re-aims your focuser so your secondary tilt adjustment is no longer correct.  So unless I'm missing something, there must be some kind of iteration between these steps.

 

Also, focuser tilt is only used here to compensate for any camera sensor tilt.  The instructions don't say how to do that, but it seems like you would need to do it with camera images, probably under the stars?  I found that focuser tilt was an essential step to getting everything aligned.  It compensates for the fact that primary adjustment re-aims the focuser, decoupling primary tilt from focuser aiming.



#38 celegroz

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Posted 03 December 2020 - 11:04 PM


 

 

6. Adjust the primary tilt using a Cheshire.  Install the Cheshire snugly in the focuser.  Look through the Cheshire "pinhole" and center the dot (the reflection of the pinhole) in the secondary mirror donut.  This is hard to explain but easy to do with precision once you see it.

 

Which Cheshire are you using? I can't seem to see the reflection of the pinhole as you describe. Here's what I'm trying to use.

 

1-IMG-0574.JPG

2-IMG-0575.JPG



#39 TinySpeck

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Posted 04 December 2020 - 12:03 PM

Which Cheshire are you using? I can't seem to see the reflection of the pinhole as you describe. Here's what I'm trying to use.

 

Just a pinhole?  Farpoint is being a little generous calling that a Cheshire, I think.  Cheshires are supposed to have an angled reflective surface inside with a cutout on the side, AFAIK, so you can shine a light on it from the side (or just use ambient) to see the reflection of the angled surface through the pinhole:

Cheshire.jpg

The picture is my 1.25" Cheshire with an Astrodon compression fitting attached to center it in a 2" focuser.  The Cheshire is a Celestron, I think I remember, and I pulled out the crosshairs at the far end from the pinhole.  Those are useful for Newtonians but just got in the way for me.

 

EDIT: I just realized your Cheshire may be usable if your scope points at a bright wall, or you have a light source shining into your OTA.  That white donut would act like my angled reflective surface, that's what you'd see reflected, but it would need to be illuminated from the OTA end rather than from the side.


Edited by TinySpeck, 04 December 2020 - 03:59 PM.


#40 pwarborg

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Posted 04 December 2020 - 02:26 PM

That's an interesting and inexpensive alternative.  Reading the instructions, though, the procedure is to adjust the secondary tilt, then the primary, and you're done.  But adjusting the primary tilt on the GSO style RC re-aims your focuser so your secondary tilt adjustment is no longer correct.  So unless I'm missing something, there must be some kind of iteration between these steps.

 

Also, focuser tilt is only used here to compensate for any camera sensor tilt.  The instructions don't say how to do that, but it seems like you would need to do it with camera images, probably under the stars?  I found that focuser tilt was an essential step to getting everything aligned.  It compensates for the fact that primary adjustment re-aims the focuser, decoupling primary tilt from focuser aiming.

I use a very simple method, which also relies on adjusting the secondary first. Just with a stiff paper disk with a centered looking hole which I put directly in the back opening of the OTA without focuser or any rings attached. I think that when you do it that way, the secondary is simply as square as it gets. Adjusting the primary doesn't change that, obviously. That's why I simply don't care if my laser touches the center of the secondary mark when I start collimating the primary, because it is clear that it CAN NOT until the primary is square with the OTA, too. Unless  the focuser is not square with the primary this is not an issue. Thus, I only look at the reflection of the laser on the target bullseye of the laser, when adjusting the primary. Comfortably from behind the OTA, laser and collimation screws right before my nose. Typically I find that when the laser reflects back to the center, it also hits the secondary mark dead center. Again, this only works when your focuser is square with the primary! If not, you need a tilt plate. I plan to make an adapter to attach my laser as close to the primary as possible (where I also use my paper disk). That way I should be able to collimate the primary and the focuser (almost) independently from each other.

Btw., to use a tilt plate to compensate for a tilted sensor in the camera seems a strange idea. With the tilt plate close to the OTA, you would put an angle (not to say a kink) into your optical path that way - and while the sensor might be perpendicular then with the optical axis, it will have a radial offset. Or so I think...

Regarding your latest edit, I also struggle to understand how to use a cheshire without light surface. I know the problem from my paper disk method. I HAVE TO shine a light into the OTA, otherwise it will not work. I tried with my flat light panel to no avail. The problem is that you need contrast between the looking hole and its surrounding. Otherwise you cannot see the reflection of it in the secondary.

Pat
 



#41 TinySpeck

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Posted 04 December 2020 - 03:58 PM

I use a very simple method, which also relies on adjusting the secondary first. Just with a stiff paper disk with a centered looking hole which I put directly in the back opening of the OTA without focuser or any rings attached. I think that when you do it that way, the secondary is simply as square as it gets. Adjusting the primary doesn't change that, obviously. That's why I simply don't care if my laser touches the center of the secondary mark when I start collimating the primary, because it is clear that it CAN NOT until the primary is square with the OTA, too. Unless  the focuser is not square with the primary this is not an issue. Thus, I only look at the reflection of the laser on the target bullseye of the laser, when adjusting the primary. Comfortably from behind the OTA, laser and collimation screws right before my nose. Typically I find that when the laser reflects back to the center, it also hits the secondary mark dead center. Again, this only works when your focuser is square with the primary! If not, you need a tilt plate. I plan to make an adapter to attach my laser as close to the primary as possible (where I also use my paper disk). That way I should be able to collimate the primary and the focuser (almost) independently from each other.

This sounds interesting but I'm having trouble picturing the whole procedure.  I don't see how the paper card and laser would be arranged.  Do you have it in a step-by-step format?



#42 celegroz

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Posted 04 December 2020 - 04:52 PM

Do you have it in a step-by-step format?

Agreed. I don't think I'm following the steps. 

 

think you're saying to install the paper blank with a center whole and adjust the primary until you see it centered in the secondary. But then I get lost on your discussion of the laser. To install the laser, I would have to install the focuser and then attempt to center it on the secondary. The only way to do this on the GSO scopes is to adjust the primary which means you'd be changing what you just set during the paper blank step. What am I missing?



#43 pwarborg

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Posted 04 December 2020 - 06:25 PM

1. Remove everything from the back of the OTA (rings, focuser, OAG, filterwheel, camera, etc.)

2. Place a stiff paper disk with perfectly centered looking hole into the back opening of the OTA.(74 mm, I think for the TS RC8, must be a good fit in any case! I make the disk with a pair of compasses, which gives me the exact center and expand the hole to about 2 mm). In contrast to a cheshire fitted in the focuser, the disk is placed as close to the primary mirror as possible.

3. Lay a little flash light into the front opening of the OTA, shining in direction of the primary.

4. Look through the hole in the paper disk and watch the reflection of the disk on the secondary mirror. You can use a DSLR with live view and zoomed display for this. It takes a bit of fiddling to find the right distance, position and angle.

5. Adjust the secondary mirror until the reflected looking hole appears dead center in the ring mark of the secondary. I consider the secondary now square to the OTA.

6. Remove the paper disk and the flashlight and point the OTA towards the floor (to avoid any potential flex).

7. Attach the focuser with collimation laser. Focuser turned all the way in. No distance rings between focuser and OTA.

8. Watch the reflected beam on the target bullseye of the laser and adjust the primary mirror until the beam hits the center of the bullseye. Done.

To check if there is any flex or "kink" in the optical train, you can put the OTA back in a horizontal position and attach the usual distance rings and pull out the focuser to about 3/4. Only if the laser point on the bullseye would significantly change position, I would attach a tilt plate and compensate. Typically, I do not need to do that.


Edited by pwarborg, 04 December 2020 - 06:28 PM.

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#44 TinySpeck

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Posted 04 December 2020 - 06:48 PM

1. Remove everything from the back of the OTA (rings, focuser, OAG, filterwheel, camera, etc.)

2. Place a stiff paper disk with perfectly centered looking hole into the back opening of the OTA.(74 mm, I think for the TS RC8, must be a good fit in any case! I make the disk with a pair of compasses, which gives me the exact center and expand the hole to about 2 mm). In contrast to a cheshire fitted in the focuser, the disk is placed as close to the primary mirror as possible.

3. Lay a little flash light into the front opening of the OTA, shining in direction of the primary.

4. Look through the hole in the paper disk and watch the reflection of the disk on the secondary mirror. You can use a DSLR with live view and zoomed display for this. It takes a bit of fiddling to find the right distance, position and angle.

5. Adjust the secondary mirror until the reflected looking hole appears dead center in the ring mark of the secondary. I consider the secondary now square to the OTA.

6. Remove the paper disk and the flashlight and point the OTA towards the floor (to avoid any potential flex).

7. Attach the focuser with collimation laser. Focuser turned all the way in. No distance rings between focuser and OTA.

8. Watch the reflected beam on the target bullseye of the laser and adjust the primary mirror until the beam hits the center of the bullseye. Done.

To check if there is any flex or "kink" in the optical train, you can put the OTA back in a horizontal position and attach the usual distance rings and pull out the focuser to about 3/4. Only if the laser point on the bullseye would significantly change position, I would attach a tilt plate and compensate. Typically, I do not need to do that.

Thanks for this complete description.  I guess a "collimation laser" has a side cutout and a bullseye?  I would think your last check would be important, since step 8 adjusts both the primary mirror tilt and the optical back tilt (where the focuser attaches), and if the mirror and back aren't quite parallel you would need to tweak focuser tilt.  Optical train imperfections would require a focuser tweak too, I think.

 

This is very clever!  I'm all geared up for the method I proposed, but if I need to change that I'll give this a try.  Have you posted this method by itself?  It's liable to get lost at the end of this thread like this.

 

I wonder if glend's link in post #36 above amounts to a commercial version of this same thing.  It didn't seem like it on reading the instructions, but maybe I didn't quite get it.



#45 pwarborg

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Posted 05 December 2020 - 03:26 AM

Thanks for this complete description.  I guess a "collimation laser" has a side cutout and a bullseye?  I would think your last check would be important, since step 8 adjusts both the primary mirror tilt and the optical back tilt (where the focuser attaches), and if the mirror and back aren't quite parallel you would need to tweak focuser tilt.  Optical train imperfections would require a focuser tweak too, I think.

 

This is very clever!  I'm all geared up for the method I proposed, but if I need to change that I'll give this a try.  Have you posted this method by itself?  It's liable to get lost at the end of this thread like this.

I didn't post it separately. There is so much out there. In the end I also just put bits and pieces together, and threw in some own thinking. I do not remember all the sources and did not want to offend people in posting MY method.

Not sure about the TS device. I've been looking at it, but it never was available and each time I looked next, the price was up again by a few euros. Maybe somebody can explain how they adjust the primary with that device? Anyway, I think it is crucial to start with the secondary with the looking hole IN the OTA opening. I couldn't think how to get the secondary square in a better way (independent from any other components). I've been thinking a lot of how to build the adjustment of the primary on this. What I describe above is the result. I am thinking about making an adapter to be able to attach a collimation laser right in the same opening at the end of the OTA, everthing else removed. This should give an even better "independent" collimation of the primary, than what I describe above. Next step would be then the focuser and all the rest of the imaging train, which would get collimation with a tilt plate, if required. Or work on a more rigid setup alltogether...

Pat


Edited by pwarborg, 05 December 2020 - 07:04 AM.


#46 pwarborg

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Posted 05 December 2020 - 07:02 AM

I wonder if glend's link in post #36 above amounts to a commercial version of this same thing.

I don't think so.They suggest the same order of events. But that device comes as 2". So, it needs the focuser attached. As explained earlier, I consider it crucial, to avoid any contribution of a misadjusted primary in my step 5. Any misadjustment of the primary will translate into a radial offset of the looking hole from the optical axis. This offset is zero on the tilting axis of the primary and increases, the further you move away from  the primary. That's why I don't like Cheshires. They need the focuser and often have a considerable length of their own, so the distance from the back of the OTA can be big enough to create significant offset. This inevitably leads to an error when you adjust the secondary this way. The disk method described above minimizes this error in staying as close to the primary as possible. You might converge eventually to a good collimation by iterating through secondary and primary adjustments with a Cheshire! But I believe the method I described does need only a single adjustment of each mirror. The one of the secondary is (almost) independent of the primary. And the primary can get good in one shot when the secondary is square.

I was thinking of also adjusting the primary while just using my disk (as the commercial thing seems to suggest). I need to still look into this. I want to avoid looking at yet another part (like the baffle tubes) which might potentially have an issue with less than optimal squareness itself. This is why I kept away from all the purely visual methods, suggesting you just need to look into the tube and make everything you see perfectly concentric. Never quite worked for me. Maybe I just still don't understand what I'm looking at... In the method I describe, I know at least what I am doing. Or so I think... smile.gif


Edited by pwarborg, 05 December 2020 - 07:07 AM.


#47 TinySpeck

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Posted 05 December 2020 - 12:59 PM

I didn't post it separately. There is so much out there. In the end I also just put bits and pieces together, and threw in some own thinking. I do not remember all the sources and did not want to offend people in posting MY method.

Aw, you're too modest!  Everyone comes up with their version by putting together pieces from other sources plus their own ingenuity.  You could call it "Pat's Anonymous Crowd-Sourced Collimation Method".  grin.gif  It's unique in my experience and looks quick, simple, and like it actually works.



#48 TinySpeck

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Posted 10 July 2021 - 12:04 PM

1. Remove everything from the back of the OTA (rings, focuser, OAG, filterwheel, camera, etc.)

2. Place a stiff paper disk with perfectly centered looking hole into the back opening of the OTA.(74 mm, I think for the TS RC8, must be a good fit in any case! I make the disk with a pair of compasses, which gives me the exact center and expand the hole to about 2 mm). In contrast to a cheshire fitted in the focuser, the disk is placed as close to the primary mirror as possible.

3. Lay a little flash light into the front opening of the OTA, shining in direction of the primary.

4. Look through the hole in the paper disk and watch the reflection of the disk on the secondary mirror. You can use a DSLR with live view and zoomed display for this. It takes a bit of fiddling to find the right distance, position and angle.

5. Adjust the secondary mirror until the reflected looking hole appears dead center in the ring mark of the secondary. I consider the secondary now square to the OTA.

6. Remove the paper disk and the flashlight and point the OTA towards the floor (to avoid any potential flex).

7. Attach the focuser with collimation laser. Focuser turned all the way in. No distance rings between focuser and OTA.

8. Watch the reflected beam on the target bullseye of the laser and adjust the primary mirror until the beam hits the center of the bullseye. Done.

To check if there is any flex or "kink" in the optical train, you can put the OTA back in a horizontal position and attach the usual distance rings and pull out the focuser to about 3/4. Only if the laser point on the bullseye would significantly change position, I would attach a tilt plate and compensate. Typically, I do not need to do that.

It came time for me to collimate again, and I did not have good success with this method.  I even machined a perfect diameter plastic disc with a perfectly centered pinhole, but a star test showed grossly asymmetrical defocused stars.

 

So then I tried the method I described originally here, but I used another laser than the Glatter.  It was difficult to ascertain the reflected spot, the procedure didn't converge well, and the collimation ended up pretty poor too.

 

Then I worked out yet another method, requiring only a Cheshire and my eyeballs.  It was easy, positive, converged in one iteration, and produced such an accurate collimation that no star tweaking was required at all.  What's that deafening silence?  The sound of the world clamoring for another GSO RC collimation procedure?  That must be it...



#49 MikeECha

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Posted 10 July 2021 - 07:51 PM

It came time for me to collimate again, and I did not have good success with this method.  I even machined a perfect diameter plastic disc with a perfectly centered pinhole, but a star test showed grossly asymmetrical defocused stars.

 

So then I tried the method I described originally here, but I used another laser than the Glatter.  It was difficult to ascertain the reflected spot, the procedure didn't converge well, and the collimation ended up pretty poor too.

 

Then I worked out yet another method, requiring only a Cheshire and my eyeballs.  It was easy, positive, converged in one iteration, and produced such an accurate collimation that no star tweaking was required at all.  What's that deafening silence?  The sound of the world clamoring for another GSO RC collimation procedure?  That must be it...

Have you seen this https://youtu.be/a3UOGDUaq6o

 

This works great for me with some tweaking because I have an AT6RC and I cant get the baffle out thru the spider. So I use a foldable mirror to look at the reflection on the secondary. I also realized in the process that I do not need a tilt plate as I can do the same thing with my GSO focuser by adjusting how it sits on its flange.



#50 dx_ron

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Posted 10 July 2021 - 07:59 PM

It came time for me to collimate again, and I did not have good success with this method.  I even machined a perfect diameter plastic disc with a perfectly centered pinhole, but a star test showed grossly asymmetrical defocused stars.

 

So then I tried the method I described originally here, but I used another laser than the Glatter.  It was difficult to ascertain the reflected spot, the procedure didn't converge well, and the collimation ended up pretty poor too.

 

Then I worked out yet another method, requiring only a Cheshire and my eyeballs.  It was easy, positive, converged in one iteration, and produced such an accurate collimation that no star tweaking was required at all.  What's that deafening silence?  The sound of the world clamoring for another GSO RC collimation procedure?  That must be it...

What!? You're just going to leave us hanging there?


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