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Equipment Discussions >> Cats & Casses

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powerstroke01
professor emeritus


Reged: 06/19/07

Loc: Western Sierra Nevada Foothill...
At10RC Collimation and CCDInspector... new
      #5699497 - 02/25/13 09:40 AM

Just wondering how well ccdinspector works. And id like to know if anyone has some instructions or a tutorial for using it???!
I did use it to analyze one picture.. Can anyone tell me about what im seeing here?



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jjongmans
super member


Reged: 02/11/12

Loc: The Netherlands
Re: At10RC Collimation and CCDInspector... [Re: powerstroke01]
      #5701026 - 02/26/13 05:14 AM

CCDInspector is useless for collimating an RC, because you only can determine it is miscollimated, but it's impossible to see what's causing the error. Is it the focuser tilt, seconday or primary? You'll need extra tools and methods like a laser (Howie Glatter with holographic attachment) and a startest.

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shiner
super member


Reged: 11/04/11

Loc: England
Re: At10RC Collimation and CCDInspector... new [Re: jjongmans]
      #5702080 - 02/26/13 04:59 PM

Interesting Mr jjongmans.
What is your opinion of this method:
http://deepspaceplace.com/gso8rccollimate.php

Would you elaborate on your procedures please?


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Jared
Postmaster
*****

Reged: 10/11/05

Loc: Piedmont, California, U.S.
Re: At10RC Collimation and CCDInspector... new [Re: powerstroke01]
      #5702456 - 02/26/13 08:54 PM

Quote:

Just wondering how well ccdinspector works. And id like to know if anyone has some instructions or a tutorial for using it???!
I did use it to analyze one picture.. Can anyone tell me about what im seeing here?





I agree that I wouldn't try to use CCD Inspector to try to perform the collimation on an RC because of the two hyperbolic surfaces, it can certainly provide feedback on whether you have things nailed. To me, it looks like you have everything nailed.

Your FWHM values are low across the field--indicating good focus, good seeing, and good collimation. Any time your Max FWHM and Min FWHM are that close together you are in pretty good shape.

The curvature amount I have never found very useful since it varies depending on the size of your CCD chip--you can't use it as a true standard of comparison. What it tells you , though, is that your stars are only 12% more bloated in the corner than they are in the center. Good enough to use the entire field.

Tilt in 'x' and 'y' tells you the difference in the amount of bloat from one corner to another. You have a miniscule amount--don't touch a thing.

The collimation value tells you the evenness of illumination across the field. You want the light falloff to match in all four corners. Yours is perfect.

If these numbers are typical for you (reproducible in multiple frames with the scope pointed in different parts of the sky) I'd say you are all set to go. You can look at your actual image to confirm that stars are tight in all four corners, but I see nothing to improve in your sample CCDInspector result.


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jjongmans
super member


Reged: 02/11/12

Loc: The Netherlands
Re: At10RC Collimation and CCDInspector... new [Re: shiner]
      #5702880 - 02/27/13 04:03 AM

Quote:

Interesting Mr jjongmans.
What is your opinion of this method:
http://deepspaceplace.com/gso8rccollimate.php

Would you elaborate on your procedures please?




The AT10RC has a design flaw; the focuser is directly connected to the primary mirror. So when you adjust the primary mirror, you'll introduce tilt in the focuser and vise versa. Here you can find a collimation ring to detach the focuser from the primary, so they can be adjusted independently.

This is my workflow:
1) Correct tilt in focuser, I use a Howie Glatter laser collimator. This laser needs to point at the center mark of the secondary.
2) Correct secondary, I use a Howie Glatter with holographic attachment; it projects concentric rings. These rings need to be projected concentric at the primary when looking in the OTA.
3) Correct primary, I center (that's important) a defocused star on the CCD and adjust the primary until the 'donut' is concentric.

When you're doing adjustments to focuser, secondary or primary, keep in mind that you have to recheck everything again. Repeat this until no adjustments are necessary and you're done. After that you can do a final check with CCDInspector to confirm collimation.


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shiner
super member


Reged: 11/04/11

Loc: England
Re: At10RC Collimation and CCDInspector... new [Re: jjongmans]
      #5702923 - 02/27/13 05:42 AM

Quote:

Quote:

Interesting Mr jjongmans.
What is your opinion of this method:
http://deepspaceplace.com/gso8rccollimate.php

Would you elaborate on your procedures please?




The AT10RC has a design flaw; the focuser is directly connected to the primary mirror. So when you adjust the primary mirror, you'll introduce tilt in the focuser and vise versa. Here you can find a collimation ring to detach the focuser from the primary, so they can be adjusted independently.

This is my workflow:
1) Correct tilt in focuser, I use a Howie Glatter laser collimator. This laser needs to point at the center mark of the secondary.
2) Correct secondary, I use a Howie Glatter with holographic attachment; it projects concentric rings. These rings need to be projected concentric at the primary when looking in the OTA.
3) Correct primary, I center (that's important) a defocused star on the CCD and adjust the primary until the 'donut' is concentric.

When you're doing adjustments to focuser, secondary or primary, keep in mind that you have to recheck everything again. Repeat this until no adjustments are necessary and you're done. After that you can do a final check with CCDInspector to confirm collimation.




Yes an interesting method and I see you have all optical centers independently adjustable when you do that? However, that woudl not work with the 8" though because the tilt plate for that model does not allow access to the mirror cell to adjust the screws with the tilter in place - Wolfi confirmed that. The 8" and 10" inch versions are different in this regard.
Teleskop-Express say he has a 8" version in development.
I will have to persevere with other methods to calibrate my own 8" RC until then - possibly the Cheshire EP method


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R3i
member


Reged: 11/25/08

Loc: UK
Re: At10RC Collimation and CCDInspector... new [Re: shiner]
      #5703040 - 02/27/13 08:27 AM

[quote
Yes an interesting method and I see you have all optical centers independently adjustable when you do that? However, that woudl not work with the 8" though because the tilt plate for that model does not allow access to the mirror cell to adjust the screws with the tilter in place - Wolfi confirmed that. The 8" and 10" inch versions are different in this regard.
Teleskop-Express say he has a 8" version in development.
I will have to persevere with other methods to calibrate my own 8" RC until then - possibly the Cheshire EP method



Surely it will work with the 8" if you are using 1 or more of the extension tubes or am I missing something? Why couldn't you screw the extension tube(s) into the primary cell then screw the tilt plate onto the exentsion tube, then finally screw the focuser onto the tilt plate? This would give you access to all the adjustment bolts.


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shiner
super member


Reged: 11/04/11

Loc: England
Re: At10RC Collimation and CCDInspector... new [Re: R3i]
      #5703132 - 02/27/13 09:43 AM

I have tried it and it does not work. The tilter device sits between the mirror cell and the extension tubes and hides the mirror cell collimation screws with the body of the tilter. On the 10 inch RC these screws are placed further away radially from the where the extension tubes screw in so is not an issue with the 10". I was even going to drill holes with my pillar drill through the tilter to get access to the screws but it wont work since the tilter screws precisely align with the screws on the mirror cell!

In your method r3i, how would you get an Allen key in there with only the 1" extension tube on? Its supposed to be collimated with the actual tubes in use and I only ever need the one 1" tube. Putting them all on to gain access is not the same thing and defeats the purpose somewhat from something that costs over $130.

Wolfi is working on a solution on an attachment that sites flush with the focuser itself to give access to the screws on teh cell and also the abiliity to adjust the focuser.

Repeat this does not apply to the 10" version since its a different design on the back.


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R3i
member


Reged: 11/25/08

Loc: UK
Re: At10RC Collimation and CCDInspector... new [Re: shiner]
      #5703703 - 02/27/13 03:29 PM

Quote:

In your method r3i, how would you get an Allen key in there with only the 1" extension tube on?




I can easily adjust the mirror cell when just a 1" extension tube is in place using Allen keys. I have the 'short end' of the key inserted into primary cell bolts and there's plenty of space.


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