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
Nançay radio telescope Nançay radio telescope The Nançay decimetric radio telescope (Le radiotélescope décimétrique de Nançay (NRT)) is located in the small commune of Nançay, two hours' drive south of Paris, France. The radio telescope saw first light in 1965, after an inauguration by the then French president, Charles de Gaulle. It is one of the largest radio telescopes in the world. The NRT is a transit instrument of the unusual Kraus-type design, with two mirrors. The flat, tilting primary mirror consists of ten panels, each 20 m long and 40 m (131 ft) high; it reflects radio waves towards the fixed secondary