Purbach is a large lunar impact crater located in the rugged southern highlands of the Moon. The distorted crater Regiomontanus is attached to the southern rim. To the northwest is Thebit and just to the northeast lies La Caille.
"The Purbach Cross"
Walther Purbach and Regiomontanus craters 1
Telescope HD Moon Video "Learn All Three '3 Crater' Patterns" 9-2-2014