Hey Nathan... I don't think you will need new glass. From all that I have read star trails are typically shot at the following settings.
f/1.4 and ISO400 = 30s
f/2.8 and ISO1600 = 30s
f/4.0 and ISO3200 = 30s
f/5.6 and ISO6400 = 30s
As your f/stop gets smaller you will have to adjust your ISO higher so noise may become an issue. I don't remember what body your shooting with to know just how much an issue with noise you might have.
If you were using a camera like my D90. Well I would need a lens with a f/2.8 or faster because noise gets to bright after ISO 1600/2000 or so.
Here is a pretty good article that I think could serve as a lesson plan.
http://petapixel.com/2013/03/18/how-to-photograph-star-trails-from-start-to-finish/