Comet Holmes 17P on October 25, 2007 as seen from Whitefish Bay, Wis. The image is a combination of two frames, one at 61 seconds to record the background stars and green halo, and one at 4 seconds to record details of the comet's core. The image was taken with a Nikon  D80 and a 500mm f/4 lens with a 1.4X teleconverter. The camera was set at ISO 400. Ernie Mastroianni photo.