Foster is a small lunar

Moon

The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 crater

Impact crater

In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

 that lies to the southeast of the larger crater Joule

Joule (crater)

Joule is a lunar impact crater that lies on the far side of the Moon. It is located to the north-northeast of the walled plain Mach. To the northwest of Joule is the crater Blazhko....

, on the far side of the Moon

Moon

The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

. The rim of Foster is slightly eroded, and the narrow inner walls slope directly down to the relatively dark interior floor. The rim has a small outward bulge along the southwest side. There is a small craterlet on the floor next to the northern rim. A tiny impact in the southeast part of the crater interior is surrounded by a small skirt of high albedo

Albedo

Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...

material, producing a bright patch.

Satellite craters

By convention these features are identified on lunar maps by placing the letter on the side of the crater mid-point that is closest to Foster.

Foster	Latitude	Longitude	Diameter
H	23.2° N	139.6° W	25 km
L	21.0° N	140.5° W	32 km
P	20.2° N	143.5° W	36 km
S	22.9° N	143.7° W	36 km