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
Discovery Channel Telescope Channel Telescope. When the comet approached Earth within 2.2 million miles (about 9 lunar distances), the size of the nucleus to be calculated to be 250 meters (820 feet) in diameter. The object was discovered by a PanSTARRS telescope, but not identified as a comet at that time. In 2017, DCT achieved 282 nights out of the year (365 days) of scheduled observations for science. At , the DCT is the fifth largest optical telescope in the continental United States, following the Hobby-Eberly Telescope segmented telescope, the Large Binocular Telescope twin telescopes, the MMT telescope, and the Hale telescope. Discovery