Ganymede transiting Jupiter, photographed by Voyager 1, 31 January 1979.  South is up.
(I’m not completely sure that it’s Ganymede: it looks like Ganymede to me, and estimating its orbital speed from the photos gives a decent match to the true value, but I’ve had issues getting moon positions to match the photos from Voyager 1’s approach to Jupiter.)

Ganymede transiting Jupiter, photographed by Voyager 1, 31 January 1979.  South is up.

(I’m not completely sure that it’s Ganymede: it looks like Ganymede to me, and estimating its orbital speed from the photos gives a decent match to the true value, but I’ve had issues getting moon positions to match the photos from Voyager 1’s approach to Jupiter.)