Here's the story: http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3280494/Main/3278322
Nice image. Question for you astronomer buff's, is Io that much bigger than Ganymede? The shadow seems pretty huge, so either there's a big size difference, or they pass real close there.
Ganymede is the largest moon in the entire Sol system, it has a mean radius of 2634.1 ± 0.3 km (0.413 Earths) Io has a mean radius of 1,821.3 km (0.286 Earths) (Wikipedia)