[leon]

Hi Guys, I am a little puzzled, at the appearance of my final combined flat.

I take them as usual, about 15 minutes on the dark side of sun set, and convert to Tiff Format in Image Plus, and then combine them in Image Plus.

I have tried Medium Combine, and Average combine, and all in between, but the end result is the same.

The captured single images are all fine, a clear and a even flat field, they just look fine, but once combined the final image has concentric rings of a different shade starting from the center right out to the edges of the frame.

Has anyone else ever experienced this, or have any suggestions , it would be much appreciated

Leon