Hi Startools friends!
here is another image! flaming star nebula
as I wrote on astrobin: the image needed more frames, fortunately the subject is incredibly beautiful!
If you noticed the unusual set of frames, here the explanation: I wanted to test which ISO is best for my camera and I planned to make 2 or 3 nights changing ISO to see which one got better results. Unfortunately we had clouds for all nights except for the first one, so my tests had to be stopped.
Here is the rationale of my ISO explorations
1. I did my homework reading all possible articles on the subject and coming to the conclusion that the right ISO for my camera is 800 or 1600 ISO
2. but I'm living in a quite polluted city so this means that I have to use single frame exposures of 1 minute or 2 minutes (at 800ISO)
3. somewhere I read that the lenght of the single frame is important too: you are giving more time to the faintest parts of your DSO to send photons to you. If you don't have signal, it is useless to average tons of frames, right?
4. so I wanted to test how much I loose in noise picking a lower ISO
ok, the temporary conclusion is that there is no significative difference between 400ISO, 800ISO and 1600ISO: after stacking and a quick post processing the image produced with 40 minutes of frames are almost of the same quality.
Most probably the explanation is that the real problem of my environment is light pollution and everything else is negligible. So, until further notice, I'll stick with 400
(please note that I did a similar test this summer with the veil which is much fainter and it seemed to me that the 400ISO stack was slightly better)