Comet 131P/ Muller January 7, 2005.
Combination of 5, 2 minute images, SBIG ST-8XE CCD.
18" f/10.5 Ritchey-Chrétien cassegrain at prime focus.
Comet 131P/ Muller is a very faint periodic comet with a large perihelion distance. It was nearly 18th magnitude when this image was taken.