1608 AD – Hans Lippershey, German-born Dutch lens maker, applied for a patent for his refracting telescope (using 2 lenses), he intended them for use in the military.
1609-1610 – Galileo Galilei built his own refractor telescopes to observe the sky, and discovered Saturn’s rings, Jupiter’s moons, and along with many other significant discoveries.
1655 – Christian Huygens, a Dutch physicist and astronomer developed powerful lenses for refractor telescopes with his new methods to polish and grind lenses. He discovered Titan, the largest moon of Saturn, and identified Saturn’s rings.
1663 – James Gregory, a Scottish mathematician, published his description of a reflecting telescope in “Optica Promota”. He never actually made the telescope which he stated in his book, as he could not find a craftsperson skilled enough to make the mirrors.
1668 – Isaac Newton developed and constructed his version of the reflecting telescope. This allowed the image being viewed to be free of chromatic aberration; the distortion of a lens that is unable to focus all colors to the same focal point; a common problem found back then in refracting telescopes.
1672 – French sculptor Sieur Guillaume Cassegrain developed the Cassegrain telescope; the first reflecting telescope.
1774 – Sir William Herschel was a well-established Newtonian-style telescope maker who discovered Uranus, two moons of Uranus and Saturn. He was the first to design and construct a giant reflector telescope, with his 40-foot telescope.
1845 – The Leviathan of Parsonstown, a Newtonian style reflecting telescope, was built in Ireland by William Parsons, 3rd Earl of Rosse - an Anglo-Irish Astronomer. It was the largest telescope ever built up to this point, and it was the first to detect the spiral arms on a galaxy.
1897 – The largest refracting telescope was built in Chicago, the Yerkes 40-Inch Refractor. It was built by Alvan Clark - an American astronomer and telescope maker - and