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
William Herschel Telescope William Herschel Telescope The William Herschel Telescope (WHT) is a optical/near-infrared reflecting telescope located at the Observatorio del Roque de los Muchachos on the island of La Palma in the Canary Islands, Spain. The telescope, which is named after William Herschel, is part of the Isaac Newton Group of Telescopes. It is funded by research councils from the United Kingdom, the Netherlands and Spain. At the time of construction in 1987, the WHT was the third largest single optical telescope in the world. It is currently the second largest in Europe, and was the final telescope constructed by Grubb Parsons