What optical device is the Dutch scientist, after whom the lunar crater Jansen is named, credited for?
Zacharias Janssen Zacharias Janssen (also Zacharias Jansen or Sacharias Jansen) (1585 – pre-1632) was a Dutch spectacle-maker from Middelburg associated with the invention of the first optical telescope. Janssen is sometimes also credited for inventing the first truly compound microscope. However, the origin of the microscope, just like the origin of the telescope, is a matter of debate.
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.