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 an 11.8 m (464 inch) wide single circular telescope and the resolution of a 22.8 m (897 inch) wide one.
An optical telescope gathers and focuses light mainly from the visible part of the electromagnetic spectrum, to create a magnified image for direct visual inspection, to make a photograph, or to collect data through electronic image sensors.
There are three primary types of optical telescope :
Mount Graham International Observatory (MGIO) is a division of Steward Observatory, the research arm for the Department of Astronomy at the University of Arizona, in the United States. It is located in southeastern Arizona's Pinaleño Mountains near Mount Graham. During development, it was first called the Columbus Project.
Construction of MGIO began in 1989. MGIO operates and maintains facilities for three scientific organizations. The first two telescopes, the Vatican Advanced Technology Telescope and the Heinrich Hertz Submillimeter Telescope began operation in 1993. The Large Binocular Telescope, one of the world's largest and most powerful optical telescopes, began operations using its mirrors independently in 2004, with joint operations between the two mirrors beginning in 2008.
This list of the largest optical reflecting telescopes with objective diameters of 3.0 metres (120 in) or greater is sorted by aperture, which is a measure of the light-gathering power and resolution of a reflecting telescope. The mirrors themselves can be larger than the aperture, and some telescopes may use aperture synthesis through interferometry. Telescopes designed to be used as optical astronomical interferometers such as the Keck I and II used together as the Keck Interferometer (up to 85 m) can reach higher resolutions, although at a narrower range of observations. When the two mirrors are on one mount, the combined mirror spacing of the Large Binocular Telescope (22.8 m) allows fuller use of the aperture synthesis.
Largest does not always equate to being the best telescopes, and overall light gathering power of the optical system can be a poor measure of a telescope's performance. Space-based telescopes, such as the Hubble Space Telescope, take advantage of being above the Earth's atmosphere to reach higher resolution and greater light gathering through longer exposure times. Location in the northern or southern hemisphere of the Earth can also limit what part of the sky can be observed, and climate conditions at the observatory site affect how often the telescope can be used each year.