Tonight I observed the Moon with the TAL 200K. The Moon was 3.86 days old, and tonight 4 large craters could be observed to the south of Mare Crisium: Langrenus, Vendelinus, Petavius and Furnerius. Tonight I decided to concentrate on Petavius.
Petavius is a complex (floor fractured) crater with the typical features of a large complex crater:
1. 177 km in diameter (large complex craters range from 50km to 300km);
2. Stair-stepped concentric terraces that drop from the rim crest to the crater floor;
3. A broad, relatively flat floor with various mounds and hills;
4. A massive central peak complex.
On the image below, you can see the terraced walls very clearly. The central peak complex rises 2500 meters above the crater floor. If you look carefully you can see a thin dark line running from the central peak complex in south-western direction towards the crater rim. This is a rille, 60 km long and 3 km wide. Schroter discovered it. The rille is part of a complex of rilles you can see on the floor of Petavius. Due to the relatively bad seeing I could not detect more rilles tonight. I could detect some small craters and hills on the crater floor. From the northern rim you can see the ejecta-blanket spreading in north-northeastern direction. On the eastern slopes of Petavius you can see an elongated feature. This is the Palitzsch Valley, formed by an alignment of several overlapping craters. The Palitzsch Valley is 110 km long. The crater Palitzsch with a diameter of 40 km forms the southern part of the Palitzsch Valley.