More flat frame overcorrection and undercorrection problems – #13 by vinvin – Siril

I’ve just wasted the best part of 4 hours retaking flat frames of various ADU ranges from 4000 to 20000 for the Oiii filter in my 294m and scope combo without success. Everything either overcorrected or undercorrects. Numerous previous occasions beforehand, too.

The closest ADU value seems to be 6000, but my calibrated images still look awful. No issues whatsoever calibrating Ha (16000 mean ADU), but always Oiii and to a much lesser extent, S2.

I’m now at the point where my time would be better spent simply applying a pixel math solution to my masterflat, but it’s completely alien language to me and the internet is if no use for elaborating either.

Can someone please point me to a simple equation to apply, as I can make no sense of this, and don’t know where to start.

Simply saying “add 0.5 to the flat” or similar advice means nothing to me without further explanation. I need a written example, please.



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