Opelt (Moon)

Named after Friedrich Wilhelm Opelt - German astronomer (1794-1863), Otto Moritz; German astronomer (1829-1912).

Opelt is the lava-flooded remnant of a lunar crater on the Mare Nubium. It lies to the north of a similar formation named Gould, and to the northeast of the prominent Bullialdus. Only a slightly raised outline remains 's rim, the interior having been inundated with lava. The rim has a wide break at the northern end and several smaller breaks to the south and southeast. (wikipedia entry)

A crater is a circular depression likely created by an impact event. On the Moon they are named after deceased scientists, polar explorers, astronauts or cosmonauts.