I took some test shots of C92 after I was finished shooting M42 the other night and decided to process them for some practice. Only a dozen or so subs stacked, im focusing on capturing m42 at the moment. I had to down-sample it to get it to upload.
The stars look terrible towards the edges, Im not at ideal backfocus distances and I think this might be causing this. I think this same problem is causing the bright double star Hatysa to cast a large offset halo flaring into the outsides of my M42 subs.
I will be correcting my backfocus distances next month hopefully.
Happy to hear any advice.
A higher quality version of the image