Thanks Andrew, mine has always produced amp glow, so will be interested to read your results.
Well, well, well, I feel like the boy that cried "wolf", here is an image of Omega centaurus taken last night with the Astro 40D and it is the best I have got for in focus across the FOV. I am at a loss as to the cause now. As for about 2 years the right side has repetedly been out of focus. This image is 16 x 2 minute exposures at ISO 800.
http://i638.photobucket.com/albums/u...s/dcd5c713.jpg