The DSLR that I use for astrophotography is the Canon EOS 5D Mark II.  It’s an amazing daytime camera and it has great low light capabilities.  Canon recently released new firmware for the 5D Mk II, version 1.2.4.  Among other things, this update includes fixes for problems with noise in long exposure bulb photos.

If you’re a 5D Mark II user, you can get the new firmware here:

http://web.canon.jp/imaging/eosd/firm-e/eos5dmk2/firmware.html