Since the Earth is constantly rotating about its axis, if you place a camera on a tripod and point it toward the north, making certain to get Polaris in the frame, and then open the shutter for about an hour or so, you'll catch an image of the stars streaking across the sky in concentric circles. The further the star is from Polaris, the longer the arc it will make. This particular image was a 1-1/2 hour exposure on Fujicolor 400 film using a Nikon F3 and a 24mm f/2.8 lens set at f/4. The sky color comes from light pollution from cities in that direction which is normally greenish, but which I have shifted toward a more pleasing purplish-blue, to mimic late twighlight even though this image was recorded around 3 o'clock in the morning.