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Image analysis for collimation

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Hello everyone,

I attached an image that came straight out of the camera. I have half of image with ok round stars and half of it with enlongated stars. I feel that either is poor collimation or the focuser is sagging a bit.. Images are 600s exposure with guiding. I recently did a polar alignment and the same day I took this image, I realigned the guiding scope with the main scope.

Anyone that had similiar issues or knows what it is, has any suggestion to make in regards to this matter?  Thank you so much



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ASTAP image inspector on a stretched frame:


To me it looks like all corners and center of the image is aberrated with what looks like astigmatism. I would say the scope is in dire need of recollimation, and not by a small amount.

2 hours ago, mcbras said:

I feel that either is poor collimation or the focuser is sagging a bit..

These are kind of the same thing in my opinion, collimation is the act of pointing the center of your camera towards the center of your primary mirror, and the other way around and when your focuser sags, the camera points off axis (bringing the scope out of collimation). If you cant make the focuser behave and be stable at all orientations throughout all of the night, you just cant have repeatable good collimation so maybe look into that if your collimation looks ok otherwise. But judging from the image i would say you have both an actual collimation error of the adjustment screws and some mechanical issues elsewhere.

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