Reflecting telescopes have been in use ever since they were invented in 1616. They have yielded some of the most beautiful and detailed images of the universe. Most of the large optical researching telescopes built since the turn of the 20th century have been reflectors. This is due to the inherent problems of creating large lenses that are used in refracting telescopes, the other common type of optical telescope.

When I lived in Pasadena I could see the top of Mt. Wilson where all the local TV stations had their antennas. Around slightly out of view from my particular location was the famous 100 inch telescope pictured here.

This is the telescope that Edwin Hubble used to discover the general expansion of the universe.