I was about to post my best-yet shot of Andromeda using the Astrotrac and found a few people were ahead of me on here. This one is taken using 100-400L at 400mm on an unmodded 7D. It's a stack (DSS) of 29 x 60s lights at ISO1600, f/5.6, and I also used darks, flats, dark flats and bias exposures to get the noise right down. I brought up colour and contrast in Photoshop, and reduced noise in Lightroom, but didn't do anything too clever.
I didn't try drift-aligning (I'll have to get to grips with that), and the stars are slightly elongated, which is a pity. The faintest stars on the full-size image are mag 17.5, which is also a new best for me, despite the slight tracking errors.
