Great work, really enjoyed it.
1/ which mode did you shoot in (P, Av, Tv, M) ?
2/ What was the aperture?
3/ did you shoot in Raw or Jpeg ?
I would always do manual for these types of things, and you usually want to shoot pretty close to wide open. If you're in a place with very little light pollution you can get away with much shorter exposures. I've gotten some amazing results shooting at f/2, ISO 1600 for 5 seconds.
I saw the OP didn't like the DP dolly, but I LOVE it. It's super easy to set up and the intervalometer is built in to the controller. You can set it up to move anywhere from .12 inches per minute to 30 inches per minute, or you can put it in SMS (shoot, move, shoot) mode and that will give you the smoothest motion possible.
You can also mount it upside down and get some really cool shots (since the track is no longer visible). This is an example of that :
Sure it's kinda pricey for the money, but it's not that bad carrying it around in a ski bag. I'm just going to ship the rail to the west coast when I fly out there.