Star Trails

I will be heading to a couple of very dark sky sites in the next few weeks. The magnitude at zenith is said to be at least 6 if not 7. So its about as dark as you can get. I want to try to hand at taking a star trail shots, but I am not sure what film to use.

For BW I have Acros and Tmax 400.

For color I have Provia, Velvia and Fuji 160NS (negative film). My guess is to forget the Velvia.

Any helpful ideas, f/stop, exposure guides would be great. I will be going at new moon so I won't have to worry about the moon being a problem.

Thank You!.

Blumine