The rescued Cocoon nebula

[gorann]

Wednesday night everything was going the right way. No moon or clouds and good guiding for once (0.5" RMS) and SQM was 21.1.

I was shooting off with my Esprit 150 and with my new ASI 071 Pro on the Cocoon nebula. Managed to make use of most of the dark time, which is still only about 7 hours up here. But next morning when I looked at the debayered images they were very very green. I finally managed to tweak the colour curves and get a decent histogram but it was hard work. I posted my problem here at SGL Discussions Cameras and Vlaiv finally found out what had happened. For some reason the white balance had been zeroed instead of the default (I am sure I did not do it - it just happened). In any case all the data was in there it was just a bit of a job to get a decent color balance. Here is the result. 81 x 5 min subs with this nice CMOS colour camera although it plays its ticks.

Thanks again Vlaiv for explaining the strange and unexpected problems of astrophotography!

[Allinthehead]

Nice result after all your issues. My stacked image is always green until i colour balance. Is this not how it should be? 

[gorann]

11 minutes ago, Allinthehead said:

Nice result after all your issues. My stacked image is always green until i colour balance. Is this not how it should be? 

Yes, maybe it is. You probably started off with a zeroed white balance while ASICAP set me off with the default setting which is Blue=99, Red=60. So I got used to a slightly pink image which was easy to balance - which I do in PS after having calibrated, debayered and stacked in PI. So when I ended up with the green one I thought that something had gone terribly wrong in the debayering and I spent the whole day trying different bayer settings. If I had known what had happened I would not have worried so much.....

This is what the debayered subs looked like (after a stretch), are yours as green as this?

[Allinthehead]

Hi Gorann. Here is a single stretched debayered image before coulour balance.

[Allinthehead]

Comparing the two, it seems you have an issue there as you can still see colour in mine. Has your image above been calibrated? You said on Astrobin that you changed the bias offset, did you get new bias frames?

The other thing is and this would be site and gear specific but your gain seems to be on the high side. I can't expose for more than 150 seconds at gain 50 without saturating the stars. I'm wondering how you could expose for 300 seconds at gain 200 without doing the same.