Hale Telescope mirror.. It was completed in 1948 and is still in active use. The Hale Telescope represented the technological limit in building large optical telescopes for over 30 years. It was the largest telescope in the world until the Russian BTA-6 was built in 1976, and the second largest until the construction of the Keck Observatory Keck 1 in 1993. Hale supervised the building of the telescopes at the Mount Wilson Observatory with grants from the Carnegie Institution of Washington: the telescope in 1908 and the telescope in 1917. These telescopes were very successful, leading to the rapid advance in understanding
Craig telescope 1852 to 1857, erected near London, England. It was a great refractor, a large refracting telescope with an achromatic doublet with an aperture of 61 cm (2 feet (24 inches)) and that was completed in 1852 in Wandsworth Common and dismantled around 1857 (although the brick tower probably survived until 1870). It had a focal length of 76–83 feet. Its namesake, the Rev. John Craig, spent a small fortune to produce a uniquely designed telescope with nearly double the aperture of the next largest refracting telescopes, making it the largest refracting telescope in the World for the better part of