He made the movie using a 13-inch telescope and a digital video camera. "Seeing was not good, so I was only able to use 250 of the 1200 frames I collected." Nevertheless, it is an extraordinary observation, showing the distant moons as genuine world-like disks as they pass in "mutual occultation."

Earth is moving through the orbital plane of Jupiter's satellites, allowing the moons to line up for events such as Wesley recorded on May 8th. This special geometry comes along approximately once every 6 years. The last time was in 2002-2003, and now it is happening again. Between April and December of 2009, observers around the world can see Jupiter's moons passing one in front of another as they circle the giant planet. As part of the International Year of Astronomy, professional astronomers are organizing a worldwide observing campaign to record as many of these events as possible.