Around the date of opposition, there are always some fine opportunities to see some of Jupiter’s moons transiting in front of or adjacent to their shadows.  Here is a compilation of good images from this year’s events. Congratulations to the observers, esp. Paulo Casquinha who captured two of them.  You can see how Ganymede’s appearance changes during its transit because of varying contrast with the jovian atmosphere behind it — and how it is relatively much brighter in the methane band because Jupiter’s atmosphere is so dark in that absorption band.