Olbers is a lunar crater that lies at the west edge of the Oceanus Procellarum, near the western limb. It lies to the northwest of the crater Hevelius, and to the north of the indistinct Hedin. Farther to the south is the crater Riccioli. Due to its location, this crater appears very oblong because of foreshortening. (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.
