Looks about how I saw it through a heavy fog in New Zealand using a borrowed 14" scope. Fog rolled in and cut of viewing in a matter of minutes. This was the last object I saw. I was going to swing over to the small cloud but the fog had other ideas. Never cleared after that. Guess I have to make another trip down under though 14 hours on a jet is too much for this old body I'm afraid.

It is best if you combine many darks to make a master and best if the temperature they are taken at is the same as the frames were done at. Of course the exposure time should be the same as well.

I don't use Registax so don't know that part. I do my calibration, dark, bias (if needed because exposure or temp or both weren't the same as the light frames) and flat field before I stack the images. This is because each frame may have to be aligned to the previous one so the hot pixels, noise and flat field issues don't line up on top of each other. If the frames were all taken at the same pointing and the guiding wasn't changed in any way and I didn't dither the image (a lot of ifs) then the calibration can be done after stacking.

Most CCD programs for taking images will do the calibration step automatically as the frame is saved if you so wish. They save both the raw and calibrated frame so you can redo the calibration later if needed (you picked the wrong darks or flat field frames, etc.).

In astro CCD language the former is "calibration" and the latter "combining". Though stacking is becoming more common and may win out.

Rick