One Hour with the Canon 1DsMkII
The image was taken with a Canon 1Ds MkII. It's a one-hour exposure, followed by a one-hour in-camera noise reduction exposure (read the article if you're not familiar with in-camera noise reduction).
I'm surprised that the 1DsMkII could make a clean exposure for one hour. Hopefully, some high-end afficianados out there (and you know who you are) could comment about their experiences with uber-long exposures with this camera.