Lat: 42.6°N, Long: 30.5°E, Diam: 33 km, Depth: 1.39 km, Rükl 14
LO-IV-091-H2 Mason is the crater near the center. The crater partially visible to its lower left is its similarly-sized companion Plana. The cookie-like mass filling the left half of the image is regarded as a volcanic dome by Schultz, 1976 (pp. 150-151).
(IAU Directions) MASON.--The more easterly of two remarkable ring-plains, situated in the highlands on the S. side of the Lacus Mortis. It is 14 miles in diameter, has a distinct crater on its S. wall, and, according to Schmidt, a crater on the W. side of the floor.
- Depth data from Kurt Fisher database
- Westfall, 2000: 1.39 km
- Cherrington, 1969: 1.92 km
- Satellite crater Mason C is on the ALPO list of banded craters
- Named for Charles Mason (1728–1786), an English astronomer. Mason's early career was spent at the Royal Greenwich Observatory near London. With English surveyor Jeremiah Dixon, Mason made one of the few successful observations of the 1761 transit of Venus. In the U.S. the pair are best known for their survey of the Mason–Dixon Line (1763–1767), separating "north" from "south". Upon returning to England Mason contributed to the Nautical Almanac and worked on perfecting the lunar tables of Tobias Mayer.
- Either Mason or Plana may have been called Longomontani by Van Langren (Whitaker, p. 196).
- Mason is Catalog number 638 in the Collated List and in Named Lunar Formations, where the name is attributed to Beer and Mädler.
- A previously undetected ridge which runs from the part of the Montes Caucasus near Eudoxus toward the southern rim of Lacus Mortis (over the couple Plana and Mason) to Williams is unofficially called Shannen Ridge by Maurice Collins (with Charles Wood co-author of the 21st Century Atlas of the Moon). The name Shannen Ridge is incorporated on chart 9 of this atlas.
- Not related to the IAU's Charles Mason, but... it might be interesting to shed light on the mysterious suicide of Arnold Caverly Mason (1906-1961). The name A.C.Mason is frequently mentioned in the very interesting book TO A ROCKY MOON from Don E. Wilhelms. - DannyCaes Dec 7, 2016