The telescope is an instrument which allows at the same time an optical enlargement of the objects observed, and an amplification of the received light of these objects, which facilitates their observation. Close to but different from the field glass, which creates this enlargement by an assembly of optical lenses, the telescope uses one or more mirrors. The invention of the field glass goes back to 1608 or 1609, and the first indisputable telescope was produced by Galileo. The first field glasses had enlargements about 30x (details on the Wikipedia page on telescopes) which however already allowed the observation of planets and their principal satellites.