Petavius is a large 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 southeast of the Mare Fecunditatis

Mare Fecunditatis

Mare Fecunditatis is a lunar mare which is 840 km in diameter. The Fecuditatis basin formed in the Pre-Nectarian epoch, while the basin material surrounding the mare is of the...

, near the southeastern lunar limb. Attached to the northwest rim is the smaller crater Wrottesley

Wrottesley (crater)

Wrottesley is a lunar impact crater that is attached to the west-northwestern rim of the larger crater Petavius, and lies along the southeast edge of Mare Fecunditatis...

. To the southeast are Palitzsch

Palitzsch (crater)

Palitzsch is a lunar crater that is located in the southeast part of the Moon, near the southeast rim of the crater Petavius. Just to the southwest of Palitzsch is Hase, while to the east-southeast is Legendre....

, Vallis Palitzsch, and Hase

Hase (crater)

Hase is a lunar crater that is located in the rugged southeast part of the Moon, to the south-southwest of the prominent walled plain Petavius. Palitzsch and Vallis Palitzsch are attached to the northeastern rim of Hase....

. Farther to the north is the large crater Vendelinus

Vendelinus (crater)

Vendelinus is an ancient lunar impact crater located on the eastern edge of Mare Fecunditatis. To the north of Vendelinus is the prominent crater Langrenus, while to the southeast is Petavius, forming a chain of prominent craters near the eastern rim...

. Petavius appears oblong when viewed from the Earth

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

 due to foreshortening.

The outer wall of Petavius is unusually wide in proportion to the diameter, and displays a double rim along the south and west sides. The height of the rim varies by as much as 50% from the lowest point, and a number of ridges radiate outwards from the rim. The convex crater floor has been resurfaced by lava

Lava

Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...

 flow, and displays a 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...

 system named the Rimae Petavius. The large central mountains are a prominent formation with multiple peaks, climbing 1.7 kilometers above the floor. A deep fracture runs from the peaks toward the southwest rim of the crater.
Rev. T. W. Webb

Thomas William Webb

The Reverend Thomas William Webb was a British astronomer. Some sources give his year of birth as 1806. The only son of a clergyman, the Rev. John Webb, he was raised and educated by his father, his mother having died while Thomas was a small child. He went to Oxford where he attended Magdalen...

 described Petavius as,

"one of the finest spots in the Moon: its grand double rampart, on east side nearly 11000 ft (3,352.8 m). High, its terraces, and convex interior with central hill and cleft, compose a magnificent landscape in the lunar morning or evening, entirely vanishing beneath a Sun risen but halfway to the meridian."

The most favorable time for viewing this feature through a telescope

Telescope

A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...

 is when the Moon is only three days old. By the fourth day the crater is nearly devoid of shadow.

70-cm radar

Radar

Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...

 images of this crater and its surroundings show that the region of the surface beyond the wide outer rampart of Petavius has a dark halo, characteristic of a smooth surface free of boulders. It is thought that this may have been created by radial outbursts during the original impact that swept the area clean.

Petavius B to the north-northwest of Petavius has a small 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...

that lies across the surface of Mare Fecunditatis.

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 Petavius.

Petavius	Latitude	Longitude	Diameter
A	26.0° S	61.6° E	5 km
B	19.9° S	57.1° E	33 km
C	27.7° S	60.1° E	11 km
D	24.0° S	64.4° E	17 km