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Is this CA or focus (or both)?
I had about 30 minutes tonight in between clouds and showers but I was determined to at least have a crack at something with my new rig. I'm trying a new F5 8" Newtonian ( a GSO) for the first time and grabbed a few short subs of 5128 and 5139 while I could. These are both DSS stacks of 4 x 30sec subs at ISO800 with a 1000D unguided on an EQ6Pro. I focused by eye to save time.
I see an artifact in the brighter stars and it looks to me like a small pimple with a blackhead in the middle. Is this just poor focus and a bit of an airy ring or is it CA. Being a Newt, I thought I'd escaped CA and merely had to worry about coma.
Any thoughts please?
Peter
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