History of the telescope
The earliest known telescope appeared in 1608 in the Netherlands when an eyeglass maker named Hans Lippershey tried to obtain a patent on one. Although Lippershey did not receive his patent, news of the new invention soon spread across Europe. The design of these early refracting telescopes consisted of a convex objective lens and a concave eyepiece. Galileo improved on this design the following year and applied it to astronomy. In 1611, Johannes Kepler described how a far more useful telescope could be made with a convex objective lens and a convex eyepiece lens and by 1655 astronomers such as Christiaan Huygens were building powerful but unwieldy Keplerian telescopes with compound eyepieces.
Zacharias Janssen
The claim that Zacharias Janssen invented the telescope and the microscope dates back to the year 1655. During that time Dutch diplomat Willem Boreel conducted an investigation trying to figure out who invented the telescope. He had a local magistrate in Middelburg follow up on a 45 year old recollection of a spectacle maker named "Hans" who told a young Boreel in 1610 about inventing the telescope. In his investigation the magistrate was contacted by a then unknown claimant, Middelburg spectacle maker Johannes Zachariassen, the son of Zacharias Janssen, who testified under oath that his father invented the telescope and the microscope as early as 1590 and that Hans Lippershey had stolen his father's invention of the telescope. This testimony seemed to convincing to Boreel, who modified his recollections, concluding that Zacharias must have been who he remembered. Boreel's conclusion that Zacharias Janssen invented the telescope a little ahead of spectacle maker Hans Lippershey was adopted by Pierre Borel in his 1656 book on the subject.