Here's a photo from last night looking back at the Hale Telescope as it was looking at the Swan Nebula (M17) in Sagittarius. The stars of the Big Dipper are descending behind the dome while Polaris, the North Star, is nearly at the center of the star trails on the right. The glow you see behind the dome is sky glow (aka light pollution) produced by the many lights of Riverside County.
The image was assembled from 25 30-second exposures. Earth's rotation over the time span produces the trailed out images of stars. A nice effect.
Here is another star-trail photo taken on a different (and moonlit) night looking in almost the opposite direction.