Jupiter is just past opposition, so that its moons and their shadows are very close together. This makes it possible for both the moon and its shadow to be in transit across the planet’s face at the same time. Tonight there’s a “double feature”: both Europa and Ganymede are in transit, as are their shadows, so that for nearly two hours all four will be in view simultaneously. Any telescope over 90mm aperture should show the shadows, and a 125mm telescope should show Ganymede as a grey disk. Europa usually disappears into the camouflage of Jupiter’s cloud tops, and requires quite a large telescope to be seen.
