My previous processing of M109 – 360x60s – did not turn out well. Serious issues with noise, most likely calibration files that were not ok.
So I did a complete re-build of the calibration files darks and bias.
The resulting stack and processed image is noticeably better:
This galaxy lies very very close to one of the bright stars of the bowl.
An integration on several nights with 60-second subs at gain 0. This resulted in a lot of (read-?) noise. I should experiment further with Gain 100.