Multi-channel/multi-session calibration question
I ran across the following.
I am executing a multi-channel and a multi-session operation in one run.
Three channels (OIII, SII and Ha) and 3 session days (every day the same three channel acquisition scheme).
All Ha and SII frames of all sessions are properly calibrated (specifically no vignetting visible anymore).
However the OIII frame calibration is somewhat peculiar.
OIII frames from one of the sessions are properly calibrated. The other two sessions are not, as strong vignetting is still visible.
I executed the calibration process several times already with a repeating outcome.
BTW the file list indicates that the appropriate calibration files have been assigned to all the lights.
How could I figure out what is going wrong?
I calibrated in PI as well. Same problem. Must be something wrong with the flats. I will shoot new ones on a rainy day as my image train remained unchanged.
I tried the remove vignetting option. But that did not work well enough. A crop and remove light pollution bypassed the problem.
So the main component of this nebula is Ha, which is green in your pallet. Or are you talking about a more general cast?
You can try HSL selective color and select green. Then using the saturation slider, go down a bit and slide the G->M (green to magenta) a bit to the right. Which should reduce the green.