An afternoon's poor sky with numerous thin clouds, ended by clearing above me, but leaving clouds along the horizon. Towards the west, it was at least thin enough to see Venus and Mars so I shot some parting shots of them. With a lot of hunting on the images at home, it was even possible to find Uranus even closer to the horizon than Mars.
With clouds hugging the horizon in all directions, the night seemed unsuited for starting a long series of exposures anywhere in the sky, so I took a quick look at Jupiter. It was already fairly well along rising in the east, but viewing conditions usually aren't very good soon after sunset on a very warm day (95°F at home).
Surprisingly, however, the sky conditions were already good enough to spot a black dot against the disk of Jupiter with my 6" refractor. I was even more surprised to find out that the dot was not the shadow of a moon, but rather the disk of the moon Callisto. Generally, the moons of Jupiter are hard to see as they cross Jupiter since they are relatively bright objects against the even brighter disk of Jupiter. Callisto, however, has a dark surface, which made it more readily visible against Jupiter's disk. ... more details and a time-lapse video of the transit ...