Using a black and white version this time to hide away the color gradients possibly caused by light leaking into primary mirrors, nevertheless I should pay more attention to the inverse vignetting since I started imaging, as the problem worsens every time when I pushed the image harder.
Equipment: Skywatcher 150/750, Nikon D5300, EQ3 Pro
Settings: 4hrs with 60s, 30s, 15s
Software: DSS, PS