Longomontanus (Moon)

Named after Christian Sorensen Longomontanus - Danish astronomer, mathematician (1562-1647).

Longomontanus is an ancient lunar impact crater located in the rugged southern highlands to the southwest of the bright ray crater Tycho. It is of the variety of large lunar formations sometimes called a "walled plain", although it is actually more of a circular depression in the surface. Because of its location, Longomontanus appears distinctly oval in shape due to foreshortening. To the southeast is the even larger formation Clavius, and to the east is Maginus. (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.