But the telescope was not the invention of scientists; rather, it was the product of craftsmen. For that reason, much of its origin is inaccessible to us since craftsmen were by and large illiterate and therefore historically often invisible.
http://galileo.rice.edu/sci/instruments/telescope.html
As early as 1611, in his Dioptrice, Johannes Kepler had shown that a telescope could also be made by combining a convex objective and a convex ocular. He pointed out that such a combination would produce an inverted image but showed that the addition of yet a third convex lens would make the image erect again.
http://galileo.rice.edu/sci/instruments/telescope.html
This report was issued in October 1608 and distributed across Europe, leading to experiments by other scientists, such as the Italian Paolo Sarpi, who received the report in November, the Englishman Thomas Harriot, who was using a six-powered telescope by the summer of 1609, and Galileo Galilei, who improved the device.
https://en.wikipedia.org/wiki/Hans_Lippershey
The earliest known working telescopes appeared in 1608 and are credited to Hans Lippershey. Among many others who claimed to have made the discovery were Zacharias Janssen, a spectacle-maker in Middelburg, and Jacob Metius of Alkmaar.
https://en.wikipedia.org/wiki/History_of_the_telescope
A typical astronomical telescope is the one made by Christiaan Huygens, in 1656. It was 23 feet long; its objective had an aperture of several inches, it magnified about 100 times, and its field of view was 17 arc-minutes.
http://galileo.rice.edu/sci/instruments/telescope.html
Hans Lippershey (1570 – buried 29 September 1619), also known as Johann Lippershey or Lipperhey, was a German-Dutch spectacle-maker. He is commonly associated with the invention of the telescope, although it is unclear if he was the first to build one.
https://en.wikipedia.org/wiki/Hans_Lippershey
His work with optical devices grew out of his work as a spectacle maker, an industry that had started in Venice and Florence in the thirteenth century, and later expanded to the Netherlands and Germany.
https://en.wikipedia.org/wiki/Hans_Lippershey
Beginning in the 1640s, the length of telescopes began to increase. From the typical Galilean telescope of 5 or 6 feet in length, astronomical telescopes rose to lengths of 15 or 20 feet by the middle of the century.
http://galileo.rice.edu/sci/instruments/telescope.html
Lippershey applied, to the States General of the Netherlands on 2 October 1608, for a patent for his instrument  for seeing things far away as if they were nearby , beating another Dutch instrument-maker's patent, Jacob Metius, by a few weeks.
https://en.wikipedia.org/wiki/Hans_Lippershey
By the early 1670s, Johannes Hevelius had built a 140-foot telescope. But such long telescopes were useless for observation: it was almost impossible to keep the lenses aligned and any wind would make the instrument flutter. After about 1675, therefore, astronomers did away with the telescope tube.
http://galileo.rice.edu/sci/instruments/telescope.html
who was the guy that invented the telescope
Hans Lippershey was the guy that invented the telescope.   The telescope was invented by Hans Lippershey.