Focas is a small
lunar impact crater that lies on the
far side of the
Moon, just past the southwestern limb. In this location the crater is occasionally brought into view due to
libration
In lunar astronomy, libration is the wagging or wavering of the Moon perceived by Earth-bound observers and caused by changes in their perspective. It permits an observer to see slightly different hemispheres of the surface at different tim ...
, but not much detail can be seen because the crater is viewed from the side.
The crater is situated in the wide valley between the ring-shaped
Montes Rook in the north and
Montes Cordillera
Montes Cordillera is a mountain range on the Moon. This feature forms the outer wall of peaks that surround the Mare Orientale impact basin, the inner ring being formed by the Montes Rook. The center of the range is located at selenographic coord ...
range in the south. These ranges form a double-ring around the
Mare Orientale impact basin. The crater is located toward the southern end of this immense feature, just to the north of the Montes Cordillera range. Focas is a relatively isolated crater, with the nearest craters of note being the
Wright–
Shaler crater pair some distance to the east along the same interior edge of the Montes Cordillera.
This is a circular crater with an interior floor about half the total diameter. It is symmetrical in form, with only some slight appearance of wear along the rim. The interior floor contains no features or impacts of note.
Focas Crater is named after
Jean-Henri Focas (1909-1969), a Greco-French
astronomer.
Satellite craters
By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Focas.
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{{Craters on the Moon: C-F
Impact craters on the Moon