I set the camera to shoot 30 second exposures, and using a cable release I set it to continually shoot photos.

This is a composite of 41 frames.

This was a test of a) if this would even work, and b) if the program I have to create the composite from all the photos would work (it did).

It looks like I am going to have to go back one night and let the camera shoot continually for much longer.

Canon 40D, set to take 30" exposures, and the drive mode set to continous shooting, cable release locked, Tamron 17-55mm XR DiII SP wide open (17mm and F2.8).

On the bottom edge of the photo, you can see the silhouette of trees, especially the lower right corner. This photo may not look like much, but to me this was a success.