Langrenus (crater on the Moon)

From wiki: Langrenus is an impact crater located near the eastern lunar limb. The feature is circular in shape, but appears oblong due to foreshortening. It lies on the eastern shore of the Mare Fecunditatis. To the south is the overlapping crater pair Vendelinus and the smaller Lamé. On December 30, 1992, Audouin Dollfus of the Observatoire de Paris observed a series of glows on the floor of this crater using the one-meter telescope. These glows changed form with time, and Dollfus expressed the belief that this was likely a gaseous emission. The cracked floor of the crater may have been the source of the gas. Flemish astronomer Michel Florent van Langren was the first person to draw a lunar map while giving names to many of the features, in 1645. He named this crater after himself; it is the only one of his named features that has retained his original designation.