Hi Folks,
I have never attempted stacking images over several nights,I have been trying to capture NGC 6357 and done so over 3 nights with over 5 hours of Data using Hyperstar on my Celestron CPC 9.25 HD Edge . However ,I have made the group stack with DSS but for some reason I am getting this Gradient that cannot be removed thru Gradient Xterminator or anything else for that matter. It looks like a rectangle shape. Possibly something to do with the stacking, not sure but I used Median for flats and Darks and Kappa sigma for light frames. However when I stack the nights separately they seem to be fine. Any ideas what is happening here. Is there a way we can manually stack the 3 together with photoshop to generate the same end result.
Group Stacked with all 3 nights together Gradient showing once you stretch the image
https://www.dropbox.com/s/4yg6mfu69e...7-All.TIF?dl=0
First night all good (No Rectangular Gradient)
https://www.dropbox.com/s/7dqinmzfli...357-1.TIF?dl=0
Second night all good (No Rectangular Gradient)
https://www.dropbox.com/s/n3fkkjym6y...357-2.TIF?dl=0
Third night all good (No Rectangular Gradient)
https://www.dropbox.com/s/yajw7iwje2...357-3.TIF?dl=0
I have put a massive amount of work here but this funny looking gradient will not go away frown.gif
Any ideas please assist
Thanks