Pettit (of the pair Nicholson-Pettit)

Lat: 27.5°S, Long: 86.6°W, Diam: 35 km, Depth: 3.91 km, Rükl 50, Eratosthenian

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Here's the reason why a "twin"-couple of pronounced craters in Mare Orientale's Rook Mountains were called Pettit and Nicholson:

In the early 1920s, Edison Pettit and Seth Nicholson made the first systematic infrared observations of celestial objects. They used a vacuum thermocouple to measure the infrared radiation and thus the temperature of the Moon which led to the theory that the Moon was covered with a thin layer of dust acting as an insulator, and also of the planets, sunspots and stars. Their temperatures measurements of nearby giant stars led to some of the first determinations of stellar diameters.

Edison Pettit (1889-1962); American astronomer active at Mount Wilson Observatory. Pettit had wide-ranging interests, and in lunar work was noted for his studies of the variation of temperatures on the lunar surface, particularly during eclipses. Wilkins and Moore also attribute a relief map of the Moon, constructed at Mount Wilson in 1930, to Pettit (their Appendix II).
This crater is not to be confused, thank you, IAU, with Petit

Nicholson, Seth B. Edison Pettit, 1889-1962 Publications of the Astronomical Society of the Pacific, Vol. 74, No. 441, p.495. (1962) (Note: the crater Nicholson lies next to Pettit on the Moon.
Pettit, Edison. The Co-Albedo of the Moon. Astrophysical Journal, vol. 102, p.14 (1945)
Pettit, Edison. Radiation Measurements on the Eclipsed Moon. Astrophysical Journal, vol. 91, p.408 (1940)
Pettit, E.; Nicholson, S. B. Lunar radiation and temperatures Astrophys. J., vol. 71, p. 102-135 (1930).
Pettit, E.; Nicholson, S. B. Temperature of the Dark Side of the Moon and of the Moon During Eclipse Publications of the Astronomical Society of the Pacific, Vol. 39, No. 230, p.227 (1927)