Since I started this thread off with a question about whether noisy banded backgrounds I was seeing with my AS1294 PRO camera at unity gain was due to some fault in the camera or because for some reason Brain wasn't recommending the right parameters for the sky conditions I thought that I'd briefly summarise my learning on these two things in case it is useful to anyone. And thanks all for the useful comments
1) Nothing wrong with my AS1294 PRO camera
. Some visible banding is expected in stretched darks at unity gain and especially with cooling switched on. 2) Therefore it is sensible to use a lot of dark frames - i.e. SC master darks comprising > 50 or so frames rather than just 5-10.
3) The apparent problems I had with Brain were user error. I hadn't appreciated how fast sky conditions were changing since making a first measurement. It is possible to start stacking frames in livestack even under very poor conditions and the 'brightness' filter is only a safeguard in so far as the first frame itself is not very dim. Changing skies mean parameters can't be optimized and marginal skies mean marginal signal to noise.
4) As Dave (turfpit) commented it also pays to use the live histogram (as well as look at the sky) to see where the signal sits relative to the left hand axis.
Anyway I have since improved the dark library and have used the SC Brain as a guide to settting gain/ exposure with (I think) pretty good results. So all seems to work now (SC dithering control works well now and also gives quite short non-wasteful settling times since I reduced the size of the dither). The main practical challenge as always has been the weather with good frames only collected during gaps in fast-moving clouds.
Anyway here is about an hour and unity gain - 110mm William apo, F 5.6 (reduced) with an Astronomik UHC filter, guided and dithered under Bortle ~ 6 skies of NGC7000. SC FWHM and brightness filter used to select raw frames for stacking. Stacking in DSS - even with Sigma stacking SC live stacks not as good as DSS at eliminating satellite streaks etc. Subs were rather short at 45s (probably didn't really need guiding at all - I think I just enjoy watching the PHD2 graph!). Intend to also try longer subs to further stack with this when conditions permit.
https://onedrive.live.com/?cid=330584F8 ... 29&o=OneUp
best wishes
Tim.
