Absolutely stunning. I don't think I've ever seen an image with longer star trails; kudos. As far as your settings, I was wondering if you used any noise reduction per shot, or if it's just straight out-of-the camera RAW files? Also, ten hours of shooting is pretty absurd -- did you somehow wire a contraption to give your camera consistent power, or did the battery grip last this long?
I shoot Jpg for several reasons. In order to keep the signal to noise ratio reasonable I don't take one long exposure, however, many much shorter exposures. This photo was compiled from about 950 concurrent exposures. With that many images it would be very difficult dealing with RAW; ending up around 8gb. Additionally, the camera must be able to save the image before the intervalometer takes the next shot. As it was, my interval was too long; looking at the full resolution, one can see gaps in the star trail.
Noise reduction isn’t necessary. When compiling the images in Photoshop, the noise actually overlaps and cancels itself. Basically I stack them together using the “lighten” option. The result ends up looking better than ISO 100, in my opinion.
As for power, I use the Nikon EH-6 AC Adapter (for the D200), connected to a portable large battery, like (not my model) [link] . I keep the battery grip in as a backup.