Tacitus is a 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...

 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...

 located to the northwest of the crater Catharina

Catharina (crater)

Catharina is an ancient lunar impact crater located in the southern highlands. It lies in a rugged stretch of land between the Rupes Altai scarp to the west and Mare Nectaris in the east. To the west-northwest is the crater Tacitus, and the lava-flooded Beaumont lies to the east along the shore of...

, at the northern extension of the Rupes Altai

Rupes Altai

Rupes Altai is an escarpment in the lunar surface that is located in the southeastern quadrant of the Moon's near side. It is named for the Altai Mountains in Asia. The selenographic coordinates of this feature are , and it has a length of about 427 km....

 ridge line. Directly west is the crater Almanon

Almanon (crater)

Almanon, named after Abbasid Caliph Al Ma'mun, is a lunar impact crater that lies in the rugged highlands in the south-central region of the Moon. It is located to the south-southeast of Abulfeda, and to the north-northeast of the smaller crater Geber...

, and to the northeast is Cyrillus

Cyrillus (crater)

Cyrillus is a lunar impact crater located on the northwest edge of Mare Nectaris. Intruding into the northeast rim is the equally large, and younger crater Theophilus. To the south is another prominent crater named Catharina. Together these three craters form a prominent trio in the southeast...

. To the southeast of Tacitus is a long chain of craters named the Catena Abulfeda. This chain runs to the northwest from the eastern edge of the Rupes Altai, continuing for over 200 kilometers.

The crater terminates a ridge which forms part of the Rupes Altai. The outer wall has a small rampart, and the interior surfaces are terraced. The rim outline has a slight polygon

Polygon

In geometry a polygon is a flat shape consisting of straight lines that are joined to form a closed chain orcircuit.A polygon is traditionally a plane figure that is bounded by a closed path, composed of a finite sequence of straight line segments...

al outline. There is a low ridge on the crater floor running from the north wall.

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 Tacitus.

Tacitus	Latitude	Longitude	Diameter
A	17.4° S	20.5° E	11 km
B	14.0° S	20.4° E	13 km
C	13.6° S	19.8° E	9 km
D	13.5° S	21.0° E	15 km
E	13.9° S	20.1° E	9 km
F	17.1° S	17.6° E	10 km
G	17.4° S	18.2° E	6 km
H	17.8° S	18.5° E	7 km
J	14.9° S	19.7° E	3 km
K	13.1° S	20.1° E	3 km
L	14.4° S	20.9° E	6 km
M	13.9° S	21.5° E	6 km
N	16.9° S	19.4° E	7 km
O	14.0° S	21.9° E	5 km
Q	18.0° S	20.5° E	5 km
R	16.7° S	19.7° E	5 km
S	14.5° S	19.1° E	10 km
X	15.8° S	18.2° E	4 km