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Image analysis -- slightly stretched stars

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Hi all, posting this on behalf of a friend, as image analysis isn't my strong suit. It's a single 90-second sub using a newly acquired but second-hand WO ZS61, and a Canon EOS 700D. To my eyes most of the stars look good, but some along the left side in particular seem a bit stretched. Would someone more experienced be able to give their opinion? Thanks!





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  • 1 month later...

HI Lee,

I just posted on a related topic since I had slightly stretched stars in a quint FRA300 and I knew my guiding, sensor squareness, polar alignment etc. were OK. Issue in my case was caused by the OAG having a difference in thickness of 1 mm! If you're friend notices this same tilt after rotating the imaging train and also proving there is no sag from imaging either size of meridian compared to being at zenith, then maybe check the consistency of thickness of any adapters being used - just a thought. It does look like classical too far from the sensor issue on the left hand side, but given you have a system that is flatfielded all ready at best focus, something else is cause that side of the sensor to be a little too far away compared to the rest of the frame.

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On 24/01/2023 at 15:08, Lee_P said:

stars look good, but some along the left side in particular seem a bit stretched


My guess is that with a bin2 stack of those, you'd be hard pressed to notice, especially if the session included a flip.
I'd stay stay right where you are.


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