Last night I attempted an observation of a double shadow transit on Jupiter. Europa started first with shadow ingress at 11:14pm PST, with transit ingress 34 minutes later. Io's shadow was to ingress at 1:37am, and transit at 1:53am. From 1:37 to 2:00am both Europa's and Io's shadows would be on Jupiter, and both moons might be visible until 2:30am. The weather was predicted to be iffy: good seeing but poor transparency due to water vapor pouring into the Bay Area, as I could clearly see on the GEOS weather satellite. It was worth a try nonetheless.
I went out at midnight to use my 12.5-inch f/7 reflector on an equatorial platform. The sky was sheeted with a thin layer of low cloud. Seeing was steady and I observed Jupiter at 340x. The sky background was bright with the cloud, but I could still see the Northern & Southern divisions in the South Equatorial Belt, the small and dark red Great Red Spot, and gradations of color in the North Equatorial Belt. All other major belts were visible. Europa's shadow was a tight black dot, and I could intermittently see the small bright disk of the moon itself.
I spent some time observing the moon, which I don't often see at this phase (waning gibbous 88% illuminated). The cloud made it appear like an old, badly exposed photograph. Many crater walls and mons appeared disconnected from the lunar surface along the terminator, especially in the area around Langrenus. I noticed rather prominent pair of hills on the edge of the moon which I think were near crater Kopff, but I am unsure. They reminded me of Mission and Monument Peaks overlooking Fremont.
Back to Jupiter at 1:15am to try to see Io's shadow. But now the cloud cover was thickening, and more clouds rippled in from the west. The air had a strange smell, like ozone but more metallic and salty. Gradually Jupiter lost more detail and it lost its color. I looked up and could not see it with my naked eye. But it was still there, eerie and vague, in my telescope. The cloud cover was just thin enough to allow me to see it through the telescope. In the eyepiece, the sky background was black, and Jupiter became a faint, solid but dark bluish-grey orb with soft edges. It looked exactly like a faint planetary nebula, but without a central star or ring structure. It was the real Ghost of Jupiter, veiled and obscure. It looked nothing like itself, and I only knew it was Jupiter because my telescope was tracking it just minutes before. NGC 3242, the planetary nebula which carries the nickname, is a lighter blue and by comparison teems with detail, with a double shell apparent with aperture, not at all like the apparition I saw. I venture not many people have seen Jupiter or other planets through cloud cover like that.
By 1:35am I lost sight of Jupiter altogether and decided to pack it in. I should have stayed out longer. When I glanced up before stepping inside, I could again see Jupiter naked eye through a narrow gap in the cloud cover. If I still had the telescope out I could have seen the two shadows.