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
3.6 m Devasthal Optical Telescope 3.6 m Devasthal Optical Telescope The 3.6m Devesthal Optical Telescope is a clear aperture Ritchey-Chretien style telescope built by Aryabhatta Research Institute of Observational Sciences(ARIES) and is located at the Devasthal Observatory site near Nainital, India. ARIES operates another 1.3m telescope at the same location. The telescope was activated remotely on March 31, 2016 by Indian Prime Minister Narendra Modi and Belgian Prime Minister Charles Michel from Brussels. The telescope optics has been built in collaboration with the Belgian firm Advanced Mechanical & Optical System (AMOS). The 3.6m DOT is currently the largest reflecting telescope in Asia. The telescope intends