At 12:31 PM 3/21/2004 EST, Bill Ferris wrote: (good stuff about shadow transits of Jupter) Early in the evening at the Arizona City site, we had pretty decent seeing, which enabled a good view of Jupiter at 365x through my 20-inch. Not knowing when the shadow was going to enter the disc of Jupiter, I was impressed by the separation between the moon and its shadow, even though Jupe is only a couple weeks past opposition, and the phase angle is quite large. Comparing the separation to that of the innermost moon and its shadow later on gave a good feel for the distances of the moons from the planet. Here's an illustration I put together using Voyager III software that illustrates the geometry. The perspective is from a bit above the ecliptic plane to show the shadow cones. http://www.psiaz.com/polakis/jupiter_shadow_cones.jpg Okay, time for some sleep... Tom -- See message header for info on list archives or unsubscribing, and please send personal replies to the author, not the list.