Actually, pretty good. You'd like to experiment by pointing at the celestial north pole (that's where Polaris, the North Star, is located), and finding an appropriate foreground to give context to the trails. When the shutter is open for a long time, sky fog (the reflected light from light sources near and far from you), becomes apparent - which is why dark sky locations are prized by amateur astronomers. Derrick's technique of stacking "short" exposures, has the benefit of recording the star trails while minimizing the sky fog.