One of Jupiter's four largest moons is passing between the sun and Jupiter casting a shadow against the giant planet. This photo was taken with a modified web cam. A total of 450 frames were taken at the speed of 15 frames per sec. through a Celestron 11in telescope working at f/10. Each frame was graded and many were discarded leaving 198 frames that were aligned and combine for a single exposure time of 13.2 sec. www.RobsAstroimaging.com