I would use Provia 100F with a f/5.6 aperture and a wide angle to normal lens. Compose with something interesting like trees, mountains, etc. Expose from 30 minutes to a few hours. You will need a dark sky for long exposures, so no Moon or city lights. Light pollution will limit your exposure times.
Kodak E200 is a good film as well. Here is a one hour shot Pentax 67, 105mm @ f/5.6 with E200 pushed 2 stops (forgive me, most of the images on the roll required this). I would only push this film one stop for star trail use and only under very dark skies. For star trails, MF film rules!