Stacking separately calibrated images

[Gavin1234]

Hi, just 2 quick questions.

I have lots of 5 min subs taken over different nights which I want to stack together. Because I’ve had to move my scope back inside at the end of each night I’ve had to do new calibration shots each night, flats, bias and darks (1st question; is that actually necessary?)

Also, can I calibrate each nights lights against the calibration frames and then align and integrate the calibrated lights? Or do I have to do a HDR composite?Hope that makes sense.

[glend (Glen)]

What sort of camera are you using? Are you shooting the same object each night? It is likely that one set of darks and bias would be fine. Many cameras, like ASI cooled CMOS are very consistent and a dark library can be used for some time provided your optics and the camera are clean. Personally, I would stick all your lights into DSS, add a set of darks and bias (which should be shot at the same temperature as you lights if the camera is cooled). Forget the flats for now. Register and stack them in DSS then do your final processing in something like Photoshop. Forget HDR.
It can be difficult to frame each night's lights exactly the same, unless your plate solving from night to night. If your doing framing manually you may get some edge of frame overlap, rotational issues, or gaps, which can be cropped out later. DSS will certainly register and stack them. Give it a try.

[ChrisV (Chris)]

And what are you using for stacking? DSS as Glen talked about or something else ?

[Gavin1234]

Yeah sorry I forgot some detail. I’m using PixInsight but I use dss sometimes. I just started plate solving last night but my manual framing was pretty good a small amount of cropping needed but not too much.

I’m using an ASI071MC cooled. All my subs have been at -20.

Since the day I got my scope I’ve had these weird spots on my images that I need flats to get rid of. I’ve cleaned the scope lens, the flattener and the camera sensor cover but it’s still there. So I always use flats, I was just wondering if I had to keep taking the every night.

I’ll make another thread to ask what the spots might be.

[Gavin1234]

Also, if I do have calibration frames from each night, is it best to make a separate image from each night or is it ok to make one master dark/flat/bias out of all the calibration shots taken over a few nights?