Answer: Galileo turned his telescope to the moon and by observing it over many nights he made an important discovery and this was a universe changing observation because it was previously believed that everything in the universe revolved around the Earth. Galileo used his telescope to advance the theory that the Earth was not the center point of creation, which the Roman Catholic Church considered "false and contrary to scripture."
Explanation: The basic tool that Galileo used was a refracting telescope. His initial version only magnified 8x but was refined to the 20x magnification he used for his observations for Sidereus nuncius. It had a convex objective lens and a concave eyepiece in a long tube.