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Alex, I set the slider at 2% the lowest available. It isn’t that; it is as if DSS is saying: “Nah, the image is too dark”. The stars are there but you have to wind up the contrast to see em. Interestingly, the faint outline of the galaxy (NGC55) is visible on the camera screen as well as the stars so my theory (built on near total ignorance of digital photography – I learned photography in the old silver halide days) is that DSS requires some minimum level of contrast between sky and stars to do its thing. But then my site does not have any light pollution as such. What it does have is a location with surrounding hills and the Murrumbidgee River about 5kms away: fogs are not all that common but otherwise clear nights can certainly sometimes look “murky”, my best astrophotography has been done on winter nights in drought.
I agree about the focus issues and I should probably do more masked test shots each night. Even with a 2X magnifier on the viewfinder my tired old eyes (even the good one) struggle to get sharp focus and sometimes even tightening of the focus lock seems to shift the focus slightly. Again, I wonder whether these bad seeing and transparency nights might create some distortion in 30s subs.
However, as Raymo says, out-of-focus doesn’t stop DSS stacking just gives you an out-of-focus stack (which is very annoying when it happens).
In summary I guess what I am asking is can I force DSS to stack light frames which have a score below its self-imposed minimum, or somehow pre-process the RAW images to push them up the luminance curve or is there some other software to try? I hate to throw away data from my relatively rare moonless and cloudless nights (proximity to the High Country gives us more cloud than further West). I apologise to city astrophotographers who have more difficulties for my whinging.
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