The Large Binocular Telescope (LBT) is an optical telescope for astronomy located on 10,700-foot (3,300 m) Mount Graham, in the Pinaleno Mountains of southeastern Arizona, United States. It is a part of the Mount Graham International Observatory. When using both 8.4 m (330 inch) wide mirrors, with centres 14.4 m apart, the LBT has the same light-gathering ability as a 11.8 m (464 inch) wide single circular telescope and the resolution of a 22.8 m (897 inch) wide one. The LBT mirrors individually are the joint second-largest optical telescope in continental North America, next to the Hobby–Eberly Telescope in West Texas. It has the largest monolithic, or non-segmented, mirror in an optical telescope. Strehl ratios of 60–90% in the infrared H band and 95% in the infrared M band have been achieved by the LBT.
