The ability for us Earthlings to see the moons of Jupiter eclipsing each other can occur only once every six years.
This six-year cycle is occurring now, in 2009, because the Earth is passing through the orbital plane of Jupiter’s satellite system.
Therefore, the natural satellites (moons) of Jupiter are positioned one after the other in a line. We see the ones in the outer orbits first, with those closer to the planet further back.
And, the last time such an arrangement occurred was in 2002/03.
In 2009, this ability for us to see and record Jupiter’s moons eclipsing each other occurs only between the months of April and December.
On May 8, 2009, Wesley, who is located in Murrumbateman, Australia, made the video with a digital video camera that was attached to his 13-inch telescope.
He recorded Jupiter’s moon Europa passing directly in front of Ganymede, one of its other moons.
Europa is the smallest of the four Galilean moons of Jupiter. Galileo Galilei discovered it in 1610, just under 400 years ago. Jupiter has 63 confirmed moons in total.
Ganymede is the largest moon of Jupiter, and the largest natural satellite of any planet in the Solar System. Galileo also discovered it in 1610. It is the largest of the Galilean moons, which are the largest moons of Jupiter.
The video showing the "mutual occulatation" of Europa and Ganymede (both passing in front of Jupiter) and the eclipsing of Ganymede by Europa is found on page two.
The video of the “mutual occultation” of the two moons in front of Jupiter and the eclipsing event of Ganymede by Europa that was recorded by Wesley is found at the SpaceWeather.com website http://spaceweather.com/.
SpaceWeather.com stated, "Nevertheless, it is an extraordinary observation, showing the distant moons as genuine world-like disks as they pass in 'mutual occultation'."
For additional information on the eclipses of the moons of Jupiter, check out the Astronomy2009.org article “The Special Project : Observing mutual phenomena of the Galilean satellites of Jupiter.”
The website is part of The International Year of Astronomy (IYA2009), which is a year-long celebration of astronomy that coincides with the 400th anniversary of the first recorded astronomical observations with a telescope by Galileo Galilei and the publication of Johannes Kepler's Astronomia nova.
The iTWire article “IYA2009: The International Year of Astronomy” contains more information on astronomy in the year 2009.
Anthony Wesley has photographed more images of the satellites of Jupiter. Check out the March 2006 Point Grey Research (PGR) article “PGR Camera Captures Jupiter.”