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What is Causing This

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#1 Doug N

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Posted 04 July 2020 - 04:07 PM

Attached is a portion of the image.  The effect is consistent across the entire field.  The exception is a very bright star in the center.  Auto-focus was used.  The scope/camera worked fine before, but we moved it to a new mount and now ...  The camera is an OSC and the telescope a refractor.

 

Thanks for any help.

 

Doug N.

Attached Thumbnails

  • Capture.JPG

Edited by Doug N, 04 July 2020 - 04:09 PM.


#2 imtl

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Posted 04 July 2020 - 04:14 PM

Doug,

 

The fact that you used auto focus does not guarantee good focusing. Your image is very out of focus. How did you use your auto focuser?

 

Eyal


Edited by imtl, 04 July 2020 - 05:00 PM.


#3 sg6

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Posted 04 July 2020 - 04:26 PM

Check the autofocuser as it looks as if well out of focus.

Maybe detach the AF and try manual ?

 

As I guess the imaging camera and the AF camera are seperate (are they) then the AF camera may have a focussed star whereas the imaging camera may not.



#4 Alex McConahay

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Posted 04 July 2020 - 04:30 PM

Yeah, you are out of focus. 

 

But you also might have some strange movement in the mount. 

 

The reason the bright star in the middle does not show the same pattern is because it is saturated, and the movement pattern is blurred. 

 

Alex



#5 Stelios

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Posted 04 July 2020 - 04:44 PM

Take a shorter exposure to minimize mount errors. Focus manually (with a Bahtinov mask). When you are trying to debug potential optical issues, you need to eliminate complicating factors first, then add them back one by one. 

 

It could be tracking + poor focus. That's the usual suspects. I wouldn't rule out some issues with the scope, but let's cross that Rubicon when and if we come to it.



#6 Peregrinatum

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Posted 04 July 2020 - 04:46 PM

are  you using a Newt?  possibly coma as well



#7 Alex McConahay

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Posted 04 July 2020 - 04:53 PM

And check collimation.

 

Alex



#8 Doug N

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Posted 04 July 2020 - 05:49 PM

Could it be optical interference because of a long nose piece?



#9 Doug N

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Posted 04 July 2020 - 05:52 PM

Refractor, not a newt.



#10 bignerdguy

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Posted 04 July 2020 - 09:43 PM

It would be best to see the entire image to know what is causing that.  As two others said, it could be collimation or coma, hard to tell simply from a portion of the image. 



#11 Doug N

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Posted 04 July 2020 - 10:39 PM

Here is the complete picture.

Attached Thumbnails

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#12 OldManSky

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Posted 05 July 2020 - 11:40 AM

Well, it's a bit out of focus...but by any chance was there a tree in the way?


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#13 bignerdguy

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Posted 06 July 2020 - 08:05 AM

Can you post the original image?  This JPEG is too blurry to see what you describe.  I can barely see a few stars that look like what your top image shows but only in one corner.  If you can somehow post the original raw image for us to look at this might help.



#14 Doug N

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Posted 21 July 2020 - 11:40 AM

So the problem has improved.  Though I still have the problem, just on a smaller scale.  It improved by shortening the nose piece on the camera.  Eliminating it really by going with threaded connections.

 

I will try to figure out how to get a link to a full image on this thread.



#15 colinrm

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Posted 21 July 2020 - 01:11 PM

I get weird stuff like that sometimes when I am slewing and autofocusing and NINA turns on guiding without me realizing it.  New part of the sky, star is no longer there, and it guides randomly on noise.




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