Interesting – I see there is a fairly bright star mixed up with the inner coma.
I can do absolute photometry on the coma using a capsule aperture.
I have first subtracted stars manually from within the coma using SalsaJ on the non-offset FITS image.
Using AstPhot32 I can go up to an aperture 200 pixels across and many hundreds of pixels in length.
This way I would not use the offset stack, which I am suspicious of because the stars are not completely eliminated.
Can you suggest what size aperture encompasses all of the coma – similar to what the eye would record?
I can make sure I go beyond that with the multi-aperture photometry.
Richard