On the edge of a fertile sea

Langrenus at the Edge of the Sea of Fertility

With the Harvest moon just past and the shadow of the setting sun approaching the eastern shore of the Sea of Fertility, crater Langrenus stands out in all its glory. Langrenus is an Eratosthenian Period crater, between one and three billion years old. This crater is about 133 km. in diameter with a rim 2.6 km. above the bright, mostly flat floor. Mountain peaks near the center stand 1 km. high. Rays from the crater can be seen projecting in a westward direction across the Sea of Fertility. Much older (four billion plus years) and slightly larger than Langrenus to the south along the terminator is the crater basin Vendelinus. The walls of this crater were dealt crushing blows delivered by the impacts that created craters Lohse, Lame  and Holden which are drawn clockwise from north to south. Many additional smaller crater impacts on Vendelinus attest to the age of this old battered basin.

More than 400 km. to the northwest, grazing angle impaction created the craters Messier and Messier A. These craters exhibit a long pair of rays extending westward across the remainder of the mare. Note the perpendicular (north-south) rays centered on Messier. Laboratory experiments have demonstrated this pattern of so called “butterfly rays” can be duplicated with shallow angle high speed impacts.

Frank McCabe

Sketching:
For this sketch I used: white copy paper 6”x 8”, and a 2HB graphite pencil
at the eyepiece with the addition of marker ink to darken shadows indoors.

Telesccope: 10 inch f/ 5.7 Dobsonian and 9mm eyepiece
Date: 10-9-2006 5:00-5:45 UT
Temperature: 10°C (50°F)
Clear
Seeing:  Pickering 5
Co longitude: 114 °
Sunset longitude: 66.1° E.
Lunation:  16.8 days
Illumination:  94%