Combining from multiple sessions, Narrowband

[jokermark]

I have the Ha, SII, and the OII all processed separately. They are not framed perfectly, how can I do a RGB mix with these and have them aligned when using Pixelmath? They don't align properly, how can I address this?

Thanks.

[sreilly]

Use Dynamic Align to align the images. Pick the one you want as a base image and align each other, one at a time and save. Then you can combine as you normally would.

[jokermark]

So align the SII, and the OII to let's say the Ha, save, then combine in Pixelmath?

[pfile]

wait, have you tried to use StarAlignment?

the best cure for this is when you register the frames for stacking, always use the same frame as the reference frame. so if you started with Ha and you pick an Ha sub to be the Ha reference, later when you do the OIII, use that Ha frame as the reference while aligning the OIII frames. then all of the stacks come out pre-aligned to one another.

rob

[jokermark]

I used to use the batch tool as I was using dslr subs. I guess I can use star alignment with my darks and flats? Otherwise I have not tried it for the 3 narrowbands...

[pfile]

say you have 1200s lights for 3 filters, Ha, OIII, SII. the bias and darks for these 3 types of lights are the same.

the only thing that differs is the flats.

the BPP script tries to match the lights with it's respective calibration frames. so in theory you should be able to throw all of your subs into the BPP script together and it will figure it out, applying the right flats. of course it needs hints: fits keywords or filename keywords describing the filter name (and the duration) in the lights and flats.

if you have lights of varying duration, it should figure that out too, either by scaling the darks (if there is only one duration of dark loaded), or by picking from the different duration darks you've loaded to find an exact, or close match to the lights being calibrated.

rob