Woollyzone wrote:

Although I haven't yet tried testing it to see if it was light leakage from
through the viewfinder, I'm pretty confident that its AG, as it matches your
description of it. Its easily cropped out, but to ensure it all goes, it
means losing about 20% of the width of the picture.

No need to crop: just subtract a dark frame from the image. Read
around:

www.google.com: dark frame

This will also remove hot pixels from the image, and even some residual
"fixed pattern noise". This dark-frame subtraction has to be done with
the raw camera data. The higher-end PhotoSlop code can probably do it,
but you can download various astronomical image processing tools for
free.

Alternatively: my 1DMk2 doesn't suffer from the problem to anywhere as
near a degree as the 10D. If the 20D/350D is the same: buy a new
camera. It's Christmas. And it's what Canon wants you to do anyways
;-)