Geological Chronicle
Stefan sits on the lunar far side just beyond the northwestern limb, spanning 112.18 kilometers in diameter. The crater lies at the approximate margin of the Coulomb-Sarton Basin, a 530-kilometer-wide impact crater of Pre-Nectarian age. Attached to its western rim is the slightly smaller crater Wegener, while Rynin lies close to its eastern rim.
Impact erosion has worn Stefan's outer rim, leaving the edge and inner wall pitted with small craterlets. The southern edge in particular has been damaged by impacts and is overlain by the bowl-shaped satellite crater Stefan L, which lies at the center of a small ray system indicative of a relatively young impact.
Stefan's interior floor forms a generally level surface marked by several impacts, notably a ring-shaped crater rim projecting through the southern half. Near the midpoint stands a low hill, possibly the buried remnant of a central peak. In 1970, the International Astronomical Union formally adopted the name Stefan in honor of Austrian physicist Josef Stefan, replacing the provisional designation Crater 100.