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.
Uraniborg Uraniborg (Danish: "Uranienborg" , Swedish: "Uraniborg" ) was a Danish astronomical observatory and alchemical laboratory established and operated by Tycho Brahe. It was built  1576 – c. 1580 on Hven, an island in the Øresund between Zealand and Scania, which at that time was part of Denmark. Shortly after its construction, the observatory was expanded with an underground facility, Stjerneborg, on an adjacent site.