Which astronomer improved the telescope in 1609 before using it to observe the sky?

Fact

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The first known telescopes appeared in the Netherlands in 1608, and Hans Lipperhey applied for a patent for a rudimentary instrument that year. Having learned of their existence, Galileo built his own models in 1609, quickly improved their magnification and aimed them towards the sky. He observed the relief of the Moon, the satellites of Jupiter, the phases of Venus and numerous stars invisible to the naked eye. These observations transformed astronomy and supported the questioning of the geocentric model. Galileo therefore did not invent the telescope, but he made it one of the first great instruments of astronomical research.