The beginning of observing season 2011. I made a piggyback bracket to ride on top of the 4 inch refractor. This was taken with a modded 40D and a Sigma 70-200mm f/2.8 zoom wide open at 200mm.
A quick trial to see how things would work. I'm moderately pleased with the results, which would benefit greatly from increased exposure time and stopping down to perhaps f/4.
An Astronomik CLS clip filter was in the camera body, needed for my light polluted back yard. (Mag 4 at best that night, with rising humidity.)
I'm thinking of picking up a 200mm f/2.8L USM II for this work, or an older 300mm f/4 L non-IS, IMHO Canon's best reasonably affordable telephoto prime.
UPDATE two days later - found one of those 300mm for sale, good price. Should have it in a week or so and then it's time for some photos.

CG5-ASGT, aligned with polar scope; 90 second subframes, darks, DSS/PS7. Flat and bias frames from a prevous session.