Clavius 58.8°S, 14.1°W

Clavius, with its diameter of 245 km and its slightly polygonal shape, is certainly one of the most spectacular complex craters on the nearside of the Moon, and therefore one of the favourite objects for observing with any size of instrument, even in binoculars or a spotting scope. Clavius is suitable as a test object for the determination of a telescope's resolution. The best observation time is shortly before First Quarter (at sunrise) or shortly after Last Quarter (at sunset), but observation is worthwhile at any time that Clavius is illuminated by the Sun. Depending on the angle of incidence of sunlight, different details of the internal structure and its crater walls are revealed. When fully illuminated (at Full Moon) Clavius becomes more or less invisible.

Clavius was formed in the Nectarian period on the lunar timescale. The southern crater wall is broken by the crater Rutherfurd (48 km, 60.9°S, 12.1°W) and the northern wall by Porter (51 km, 56.1°S, 10.1°). Both craters exhibit central mountain massifs. Between Rutherfurd and Porter on the crater floor there are low ridges, like mare wrinkle ridges. Beginning at Rutherfurd, a chain of craters, gradually decreasing in size, stretches in an arc towards the west: Clavius D, then Clavius C, N and J (21 km, 13 km and 12 km, respectively). Clavius D, the largest of these secondary craters has a diameter of about 25 km. On the southern floor of the crater, near the inner crater wall, larger telescopes show dozens of craterlets and crater pits.