Registering mono frames in PixInsight

[AMcD]

When registering mono frames in PixInsight, is it better (a) to use the best frame from the channel being registered as the reference frame for that channel or (b) to use the best single frame from amongst all the channels as the reference frame for each channel, to ensure that each stack is registered against the same reference.

When I tried option (b), I got a result with black haloes around the stars and poor eradication of satellite trails etc. which has made me wonder whether I should be using option (a).  

Apologies if I have not articulated the question sufficiently clearly!

[scotty38]

When I have tried registering per channel I end up with the channels not aligning properly when they get combined. I accept there are probably other steps I should take but I just resorted to choosing one frame from the whole lot and that seems to work ok for me.

Could it be better? Not sure 🙂

[david_taurus83]

You would be better to use one frame for aligning them all. Any edge artifacts can be more easily cropped out afterwards. If you align by individual channel you can end up cropping more out after you manually align. I can't say ive seen any strange artifacts by doing option b though. I would have thought your issues would be more down to the pixel rejection algorithm chosen when stacking.

Edited November 22, 2022 by david_taurus83

[scotty38]

Latest WBPP now includes "Autocrop" which retains the astrometric solution. Cropped and uncropped masters are now saved as output. Obviously this can be turned off too.