Hevelius’ labeled map of the Moon

Courtesy the United States Naval Observatory

Hevelius gave the features on his Moon maps Earth-like names, such as sea, or “mare” in Latin. Hevelius discovered the Moon’s “libration,” which is the slight wobble that allows us to sometimes see a tiny part of the Moon’s far side. The dotted lines in this image from his 1647 atlas of the Moon, the Selenographia, show those areas that are sometimes out of view around the Moon’s edge.