What optical device is the Dutch scientist, after whom the lunar crater Jansen is named, credited for?
Jansen (crater) Jansen is a lunar crater in the north part of the Mare Tranquillitatis, named after Zacharias Janssen. It is located to the east-southeast of the crater Plinius. The rim of Jansen is low and narrow, with a notch along the western edge. The interior is relatively level, which may indicate it has been covered by lava. To the south-southwest a small but prominent crater lies on the crater floor, halfway between the center and the rim, further southeast is a small but prominent crater named Sinas.
Hermann Joseph Klein Hermann Joseph Klein (September 14, 1844 – July 1, 1914) was a German astronomer, author and professor. Born in Cologne, Germany on September 14, 1844, he attained his doctorate from the University of Cologne in 1874, and taught at the school. He was a member of the Selenographic Society and the crater Klein on the Moon is now named after him.