How has the refracting telescope had an impact on astronomy?
It is interesting to note that for about 1500 years, the modern thought of astronomy held the belief that Earth was the center of the known universe, and that all the planets and the sun revolved around the Earth. This was known as the Ptolemaic theory, after Claudius Polemy, a Roman teacher-philosopher who wrote his treatises in Greek. Then, a fellow named Copernicus decided the sun was the center of the universe, and the Earth and the other planets revolved around the sun. All this was going on about the time a fellow named Galileo Galilei put to use the first optical telescope, and observed four moons orbiting the planet of Jupiter.
Since that time, various improvements have been made in optical telescopes, improving their ability to refine the images they strive to bring into sharp focus here on Earth. The most recent development of mention is the Hubble Space Telescope, which orbits Earth and provides much sharper images without the obstruction of the atmosphere and light pollution the Earths surface provides.