Triple Transit, looked like four!

11" SCT, 233x
8:00p.m. - midnight PST

Amazing! First, the Callisto shadow began its transit around 8:50 p.m. local time. About an hour later, Ganymede began its transit across the face of Jupiter and was so dark, it looked like another shadow transit. It remained this way all the way across the disk. At about 11:00 p.m. local time Io began its transit in front of Jupiter but I lost it soon after. (Why was it so hard to track and Ganymede so easy?)

Io's shadow crept onto the disk a half hour later. Right then, it looked like a triple shadow transit. Finally, at about midnight local time Ganymede's shadow edged onto the face of Jupiter and it looked like four shadow transits at the same time. Amazing!!

Ed

P.S. I added a screen capture from SkyTools2 to show what I saw. Io is shown, but I couldn't see it :-(

Attached Image:

I observed the Galilean moon events tonight with the 6" TMB, binoviewer, 1.7x corrector and dual 10mm supermonocentric eyepieces for about 204x magnification. The binoviewer works some mojo on the brain, so the image scale is surprisingly generous at this magnification. I've never seen any moon events before despite observing Jupiter on probably 50 nights in the last 4 years.

At one time tonight I saw 4 objects on the disc of Jupiter simultaneously - the shadows of Ganymede, Callisto, and Io, as well as the moon Ganymede. And bummer - I could have bagged 5 objects at once if I'd only consulted my chart before hand and knew where to look for the moon Io. Here was tonights greatest moment for sure:
http://www.eagleriver.com/tmb152/jupe.gif

Once I knew where the disc of Io was, it was easy to spot now and then, but Callistos shadow had egressed by then.

The shadows stood out like sore thumbs. Seeing Ganymede shadow ingress simultaneous with Callisto shadow egress was too cool. Ganymedes shadow is big. Ganymede itself stood out well. I could see the moon Io now and then, though it was impossible to hold in sight for very long as the seeing was quite variable. As far as contrast against the planet, I'd give the shadows a 10, the moon Ganymede a 7, and the moon Io gets a 2 or 3. During moments of greatest seeing shadows were inky black circles.