I'm one of the astronomers who put the thing together - thanks for the interest!
We use standard SBIG off the shelf astronomical cameras as detectors. The lenses are fast enough, and the integration times long enough, that read noise is negligible even with only modest cooling of the detectors.
We've published a paper that describes the thing; this is the publicly available version, for those who are interested:http://arxiv.org/abs/1401.5473
As you may notice we're mostly concerned with scattered light; we measured the point spread function out to ~1 degree (Fig 6) and found that it is amazingly well controlled (this was recently confirmed by another group, who compared our results to a wide range of other telescopes).
We've had some science results out this year, too - and we just put out a press release on the discovery of seven very faint galaxies (which might be why CR posted it today!). The reason why we went with Canon is that I'm a Canon shooter (with a special interest in dragonflies..) and I was aware of the quality of the updated lenses. I know lenses and Bob knows telescopes, so it all worked really well.
Other groups have used Canon lenses for astronomical purposes, but typically just to cover a wide area of sky - not to detect very low surface brightness emission, beyond the reach of reflecting telescopes.
Anyway, sorry for rambling on - it's a fun project!