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:
![](https://i0.wp.com/www.drogenberg.be/wp-content/uploads/2021/05/M109_Newstack_dark_bias-mod-St-V2.jpg?resize=525%2C320&ssl=1)