Amalthea: the last of its kind

This moon of jupiter was the last moon in our solar system to be detected via eye in the telescope.

According to wikipedia:

Amalthea was discovered on 9 September 1892, by Edward Emerson Barnard using the 36 inch (91 cm) refractor telescope at Lick Observatory. It was the last planetary satellite to be discovered by direct visual observation (as opposed to photographically) and was the first new satellite of Jupiter since Galileo Galilei's discovery of the Galilean satellites in 1610

Since the probes etc. have done a pretty thorough scouting, it is unlikely that anything more could be discovered in this way.

By NASA / JPL - http://photojournal.jpl.nasa.gov/catalog/PIA02532, Public Domain, Link