Yesterday night I shot the NGC 3372 area with a 85mm f/1.8 squeezed to f/2.5. I used an unmodded Canon 6d and took 30 frames of 10 seconds each. Light pollution of 30km away Cape Town did not allow to expose longer on 6400 asa. So I took 30 frames.
The result appeared weird as the bottom of the image has some yellow discoloration while the original; cr2 frames did not have this.
Does anybody know what might cause the gradient ?
30 frames, 4 darks, 6 flats stacked with Deepskystacker 3.33.
http://pix.skysurfer.eu/ngc3372-30x10sec.jpg