I thought its called a grazing lunar occultation but im not sure what its called now. 1st July 2008. I saw IO go in front of Jupiter at around 0015hrs, then I lost it, I tried a number of different filter combinations actually just RED and YELLOW, for about 2 hours, but it was too small to be seen, let alone any shadow, what was i thinking! then it came out the other side.

anyway found a nice pic on the cloudy nights forum, taken with a proper imager. I think as the name implies its easier to catch it grazing on the edges than anything else.