A long exposure of M31 to get the very faint envelope visible with a good signal to noise ratio.
It sounds quite weird but M31 is a difficult object.
The dynamic range is huge but I gave it a try.
LRGB = 300:357:167:300 minutes.
The 167 minutes for green was a little mistake.
I put in 100 times 100 seconds instead of 100 times 180 seconds.
Mike