M33, 1 hour 45 min

This is 1 hour and 45 minutes of M33 taken with the Sky 90 at f/4.5 with an st-2000 and SBIG clear filter. Flat and dark reduced and stacked in CCDSoft, further processing in Photoshop. Subframes were 5 minutes each.


Is this gradient (lower left to upper right) typical for light pollution in a widefield image shot in moderate light pollution, or is there something else at work here??? Frames are flat and dark subtracted.