Large Binocular Telescope (LBT) is an astronomical observatory on Mount Graham in Arizona that is built like a giant pair of binoculars. The LBT consists of two identical telescopes connected side by side. Together, they make up one of the largest visible-light telescopes in the world. The LBT lies about 75 miles (120 kilometers) northeast of Tucson. Scientists in Italy, Germany, and the United States worked together to build the observatory.
Each of the LBT’s twin telescopes gathers light through its own large primary (main) mirror, which measures 27.6 feet (8.4 meters) in diameter. The two primary mirrors were created at the University of Arizona’s Steward Observatory Mirror Laboratory in Tucson. Workers there cast the two glass discs with a honeycomb structure to make them stiff and lightweight. They then polished their curved surfaces to a mirror finish. Each primary mirror reflects light onto a smaller secondary mirror. The thin, flexible secondary mirrors measure only about 1/16 inch (1.6 millimeters) thick, enabling an adaptive optics system to continuously adjust their shape. Adaptive optics systems correct for the blurring effects of Earth’s atmosphere (see Telescope (Adaptive optics systems) ). Other optics are designed to combine the light from the two telescopes and direct it into cameras and other instruments.
Astronomers took their first images using both mirrors of the LBT in 2008. In 2012, scientists began using new adaptive optics to combine the light from the twin telescopes to greatly increase the LBT’s resolution. Resolution is the ability to produce images with sharp detail. The linked telescopes currently have the same resolution as would a single, giant telescope with a primary mirror 74.8 feet (22.8 meters) in diameter—larger than any ever built. Such high resolution enables astronomers to study extremely faint objects, such as planets orbiting nearby sunlike stars and distant galaxies that formed early in the history of the universe.
See also Telescope (Honeycomb mirrors) .
