[JohnH]

I have been using ICNR for a while as I was having difficulty with dark farmes not removing amp glow or handling warm/cool pixels well. I have attached a couple of frames to show you what I mean, they are both at iso 800 with a Canon 20d. The ICNR is a stack of 11*300s (total of 110 mins of "sky" time), stacked and aligned in IP 2.8 then I used Auto in the DD option - I realise this overcooks it but wanted to show up the noise, finally loaded into PS, scaled down to 25% and saved as a JPEG at about 190Kb ... it looks a bit grainy but not bad....

The second shot is 19*360s (114 mins of "sky" time). Processing steps taken were identical, amp glow, band of red, streaks in the nebulosity. In short pretty horrid.

Is this normal?

My (16) darks were taken (outside) at the end of the imaging session, of course the temp was not identical but I cannot control temp so is there a better way to process these? I have read about adaptive dark frame matching but am uncertain as to how this is perfomed in IP.

Pretty conclusive from my pov - for longer (> 3 mins) exposures with a 20d ICNR is better.

From my previous work I believe I might be better with darks at <180s but I cannot prove this. Overall therefore I suspect my best option is 1600 iso, sticking to 3 mins exposures and stacking more frames perhaps shooting darks at the meridian flip or when switching targets (ie in the middle of a session?).