Question: What optical device is the Dutch scientist, after whom the lunar crater Jansen is named, credited for? 
Sentence (from "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.
Relevant evidence: Yes