Saguaro sky

Circular star trails fill the upper three-fourths of the image, concentrating around Polaris, the North Star, just above the center of the image. Directly beneath Polaris is the silhouette of a saguaro cactus, standing amid a desert landscape.

Chris Cook, from East Dennis, Massachusetts

The night sky spins above the landscape of Kofa National Wildlife Refuge in Arizona in this 8-hour star trail shot. The imager used a DLSR to take 30-second exposures at f/4 and ISO 5000.