Chacornac is an irregular lunar impact 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...

 attached to the southeast rim of the crater Posidonius

Posidonius (crater)

Posidonius is a lunar impact crater that is located on the western edge of Mare Serenitatis, to the south of Lacus Somniorum. The crater Chacornac is attached to the southeast rim, and to the north is Daniell....

. It lies just to the east of the Mare Serenitatis

Mare Serenitatis

Mare Serenitatis is a lunar mare that sits just to the east of Mare Imbrium on the Moon.It is located within the Serenitatis basin, which is of the Nectarian epoch. The material surrounding the mare is of the Lower Imbrian epoch, while the mare material is of the Upper Imbrian epoch...

, and north of the crater Le Monnier

Le Monnier (crater)

Le Monnier is the remnant of a lunar crater that has been partly inundated by lava flows. It is located on the eastern edge of Mare Serenitatis, and the western part of the rim is missing so that it now forms a large bay. To the north is the crater Chacornac....

.

The rim of Chacornac has a somewhat distorted, pentagon

Pentagon

In geometry, a pentagon is any five-sided polygon. A pentagon may be simple or self-intersecting. The sum of the internal angles in a simple pentagon is 540°. A pentagram is an example of a self-intersecting pentagon.- Regular pentagons :In a regular pentagon, all sides are equal in length and...

al outline, and appears uneven, especially in the northwest where it is attached to the rim of Posidonius. The flooded floor is irregular and uneven, and contains a system of faint rille

Rille

Rille is typically used to describe any of the long, narrow depressions in the lunar surface that resemble channels. Typically a rille can be up to several kilometers wide and hundreds of kilometers in length...

s called the Rimae Charocnac. There is no central peak, and no trace of a ray system

Ray system

A ray system comprises radial streaks of fine ejecta thrown out during the formation of an impact crater, looking a bit like many thin spokes coming from the hub of a wheel. The rays can extend for lengths up to several times the diameter of their originating crater, and are often accompanied by...

. The ground around the crater is rugged, with a hilly, sloping rampart to the west.

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 Chacornac.

Chacornac	Latitude	Longitude	Diameter
A	29.8° N	31.5° E	5 km
B	29.8° N	31.9° E	6 km
C	30.8° N	32.6° E	4 km
D	30.6° N	33.6° E	26 km
E	29.4° N	33.7° E	22 km
F	29.2° N	32.9° E	26 km