Final result with the sides cropped to cut off the corner vignetting. North is to the right. 31x3-minute exposures at ISO 1250. 93-minutes total integration time. Dark subtracted and flat-fielded. The Master Dark was a stack of 10 frames, the Master Flat a stack of 4 pointing at a blue dawn sky. I calculate that I should be able to achieve a similar result (in terms of SNR) with only 10-minutes total integration time at a dark site, using the same camera. That should cut down to under a couple of minutes if the camera had identical sensitivity/noise characteristics and no colour filtration at all (i.e. similar to a typical astro CCD when it is used to take the L-frames in an LRGB set). Sometimes one hears of how "fast" chilled astro-CCDs are, quite often not comparing like with like. From 93-minutes to under 2-minutes allows for a lot of comparing apples to oranges ;-)

So did the tracking work? To an extent, yes. But nowhere near good enough at the 1:1 pixel level. The above image is about the size of a 4x4 binned image for this camera. By the way, I also tried binning 4x4 in post-processing but the final result was not significantly less noisy. Guiding problem: the autoguider sees 3 arc-seconds per pixel, but the Canon 1Ds sees 0.46 arc-seconds per pixel. IMHO that sounds rather ambitiuos, hoping to keep within + - 0.15 pixels in the guider. It does keep things quite well within half a pixel, but not quite within 0.2 pixels. One could try a longer focal length guide scope, better an off-axis guider, but then average seeing is supposed to be around 1 to 2 arc-seconds anyway (that's 2 to 4 pixels across in the 1Ds!). There's a bit of a drift in the image and perhaps more practice can get the stars to become more rounded.

Another aspect I checked was to see if my polar alignment was good enough. I had simply used the CGE's polar alignment routine. Surprisingly, I could not detect any field rotation between my first frame and the last. Yes, I had to "translate" them to align them, but no "rotation" was required (derotating in post processing). I view this as pure luck, since on other nights I did have to derotate frames before stacking, e.g. to stack 59 x 5-minute frames of M45, next.