Geological Chronicle
Helmholtz is an impact crater measuring 110.16 kilometers in diameter, located near the south-southeast limb of the Moon. Attached to its south-southeast rim is the somewhat smaller crater Neumayer, while the larger crater Boussingault is nearly attached to the west-southwestern rim. The crater is named after German physicist and physician Hermann von Helmholtz.
The outer rim of Helmholtz is worn and rounded, though not significantly disrupted, and the perimeter edge can still be discerned. Several small craters lie along the inner edge: one crater spans the inner southeast wall, a pair occupies the opposite wall to the northeast, and a couple of smaller craterlets lie just inside the north rim.
The northern half of the interior floor is level, marked only by a few very tiny craterlets. The southern floor is more irregular due to overlaying ejecta from Neumayer and Boussingault, and is marked by a pair of tiny craters in the southeast. Across the interior, there is no central peak.