The answer to this is Galileo Galielei, the famous Italian scientist.
He did not actually invent the first telescope, but he was the first one to use a telescope to do a lot of astronomical observations. He was the one who used a telescope to discover, among other things, that there were four moons of Jupiter.
Galileo was able to infer that there were moons around Jupiter because he saw these four points of light around the planet that moved around it in ways that seemed to indicate that they were orbiting.
Four centuries ago, in the Netherlands, it had began to talk about achieving of a lens device through which the considerable distances could be seen. Initially, having poor performance, the invention has evolved rapidly, becoming a high-precision optical instrument, able even to track satellites of Jupiter. Today, people consider the Dutchman Hans Lippershey as the first man who had assembled, in 1608, the lenses so he could see close objects, although Galileo Galilei was credited as the inventor of the telescope. And yet, perhaps, to neither of these scientists, does not belong the paternity of telescope discovery.
The true inventor of the telescope could be, according to the latest historical assumptions, a modest Spanish merchant, Juan Roget, who died between 1617 and 1624. His idea has not been received well in his country of origin, but paradoxically, in another country located in a full war with the Spanish Empire - Netherlands, where three individuals have stolen the idea - believes the British historian Nick Pelling.