Marc,
Quote:
Originally Posted by multiweb
1_ Why am I getting purple halos around the brightest stars? Is it a focus issue?
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You mention you're friends refractor - what was it? Was it a achromat by any chance? At a quick glance it looks like a chromatic aberration issue. Potentially compounded by soft focus.
Quote:
Originally Posted by multiweb
2_ Some stars on the edge of the field have really weird shapes too. Why is that?
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The weird shaped stars around the edge look like a field rotation problem due to inaccurate polar alignment. You can see them rotate in a small arc.
You'll need much greater data for the Selective Contrast Masking (highpass filter) to work. Focus on achieving good polar alignment and sharp focus first, then progress from there.