Alphonsus (Moon)

Named after Alfonso X (El Sabio) Alphonsus - Spanish astronomer (1221-1284).

Alphonsus is an ancient impact crater that dates from the pre-Nectarian era. It is located on the lunar highlands on the eastern end of Mare Nubium, west of the Imbrian Highlands, and slightly overlaps the crater Ptolemaeus to the north. To the northwest is the smaller Alpetragius. (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.