Large halo around target after stacking

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Chase Davidson avatar
Hi everyone, I’ve taken ~5 hours of 5 min Sii subs of the Pac-Man Nebula with my 130mm refractor and asi2600mm. I ran subform selector in pixinsight with the parameter that eccentricity <7 to filter out the initial bad frames and then blinked the remaining frames that looked bright. I live in south Texas so many of my subs start to show signs of dew formation on the lens sometime towards the end of the night.  I usually throw those out immediately. 

This time around I ended with just over 3 hours of usable data that all looked good in blink. After stacking with my other Oiii and Ha data in WBPP, my Sii master frame looks like it has a terrible halo around the Nebula. Am I missing some extremely bad dew sub frames? Would dynamic background extraction remove this (probably night, right?) Is there anything else that could be causing the halo? See attached picture of my master light Sii shot after initial stretch. 

any help would be greatly appreciated!
-Chase
Engaging
Brian Puhl avatar
Kinda looks like dew to me.    Small chance it could be flats.  Rule that out by simply stacking without.  

Background extraction utilizing division method might work, but I'd use that as an absolute last resort.
Chase Davidson avatar
Went back and looked at my subs and couldn’t see any dew in my lights but just so happen to check out my flats for that day and they are horribly dewed up! Good call, thank you!

-Chase
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