|Green filter sub-exposure. Note the remaining dust rings on the background.|
Ups. I discovered that my calibrated green filter subexposures suffer from remnant dust rings which are visible on the background at high contrast setting.
Suspecting MaxIm's auto-calibrate I tried to calibrate manually but it made no difference. Something must be wrong with my flats - what I do not know. I will ignore this for the time being and sort as usual. Will use 13 out of 32 subexposures. I rejected due to high background values (from passing haze) or due to fading of the M100 arm visibility.
Note: two different exposure times were used on the selected 13 sub-exposures: 1200sec and 900sec. That was not wise and will cost me when doing further processing. Still, despite these problems with my green data, I will press on.