According to Discovery, Sir Isaac Newton invented the reflecting telescope, which was used to view and map out the orbits of the planets. He also used his theory of gravity to accurately calculate the elliptical orbits of planets around the sun.
Before the reflecting telescope, scientists relied on refracting telescopes, which produced inferior images. By replacing the mirrors in the refracting telescope with lenses, Newton created a much more powerful and compact telescope.
Sir Isaac Newton earned membership to the Royal Academy when his mentor, Isaac Barrow, presented his invention to the scientific community. As of 2014, the Newtonian telescope remains a very popular design.