Skies in Palo Alto stayed clear just long enough to see the beginning of the Io transit on Jupiter from 2:15 to 2:45 am. This was a particularly interesting event since the transit occurred so close to Jupiter's opposition that the moon's shadow was almost directly under the moon. My list of Jupiter events showed the moon transit and shadow transit beginning at exactly the same time, so I wasn't sure what to expect visually. Io looked like a bright BB superimposed on the planet. It's shadow was visible as a dark outline on the Northern and following side of Io itself, looking more like a black eye rimming one side of the moon than a normal circular shadow. Both the moon and its unusual, partially obscured shadow were constantly visible under fairly steady viewing conditions with a 7 inch Dob.
Up until last night, the shadows of the Galilean satellites have been located on the preceding side of the moons during this seasons transits of Jupiter. Earth caught up with and passed Jupiter at 6 pm last night (opposition). Only eight hours later, it was clear that the shadows of the Galilean satellites had shifted to the other side of the satellites. As Earth moves further from Jupiter over the next week, the separation between moons and shadows during transits will now get larger and larger.
Fun to be able to gauge the positions of Earth and Jupiter by the play of light and shadow of the moons. The forecast looks dismal for the next well placed Io transit on Wed evening, so I'm glad I got a chance to see this last night.