M31 despite full moon, but annoying artifact

[IDM]

Hi,

Clear nights have been so rare that despite the full moon I had a go at capturing M31 with my new Altair 26C camera attached to an Esprit 100 with field flattener.

Clouds still kept rolling through so out of a whole evening I managed to get keep 82 1 minute subs. The result is below. the subs were stacked and processed in Siril. Annoyingly there is a weird artefact which can be seen. This appears as a dark spot in the flats, but hasn't calibrated out. I checked the camera and all the telescope lenses and there was no obvious dust. I am interested in feedback on the image and any ideas on the artifact.

Thanks,

Ian

[ONIKKINEN]

As feedback i think your image looks pretty good for such a short integration, but colour calibration could take another look for this one. Try the photometric colour calibration tool in Siril, and maybe SCNR green if necessary (not always the case). Could just be a little bit too much saturation if you did do PCC.

Dust can move between your lights and flats, so its possible it just wasnt removable this time. Did you take flats directly at the end of the session without removing the camera from the scope? If you moved the kit inbetween your lights and flats you will also get bad calibration.

[tomato]

That's a great "full moon" M31. It will always be hard to achieve a reasonable  background and good colour balance with so short an integration time and the moon illuminating your subs. I how found that a big chunk of dust right on the camera sensor window will be difficult to calibrate out, even with flats. Big dust particles can move without any help so the problem may have gone away.

[IDM]

4 hours ago, ONIKKINEN said:

Did you take flats directly at the end of the session without removing the camera from the scope? If you moved the kit inbetween your lights and flats you will also get bad calibration.

Hi,

I took the calibration shots the following day, but the camera nd scope remain connected and untouched until I have the calibration done. 

I think I will invest in an air spray just to check that the sensor is ok before my next outing (not tonight as its cloudy and snowing despite the clear forecast  😕