This was my first try at doing a long exposure on a digital camera of the night sky. An external timer was used to keep the shutter open for 45 minutes.
Even after touch up post processing, the image is very, very noisy. The noise floor on most sensors has quite a bit to do with how warm they get. Folks go to extremes to get their sensors cold, the most typical solution is to use a TEC/Peltier junction. One issue with these chillers is that they only push heat to the other side of the plate - - you still need to get it out of the system somehow; this is typically done with large heatsinks and fans.
I found a company which will modify your stock DSLR to have a chiller, but it's a very expensive prospect, on the order of 3 grand. I think I may try modifying a cheap point and shoot camera first to see what sort of results I can get... if I can find one which will let me take long exposures. For now, I'm going to make sure I get my camera to take a black reference first (doh*), but this effectively doubles the time it takes to do a shot, as the exposure time has to be the same for the black reference.
Anyway, here's my first attempt at this:
This was shot on a 5d mark II, using a 24mm f1.4 prime lens. I'm happy with the result, but I crave less noise.