Multiple Mirror Telescope (MMT)

A telescope of unique design which operated at the Fred Lawrence Whipple Observatory on Mount Hopkins in Arizona between 1977 and 1997 as a joint venture of the Smithsonian Institution Astrophysical Observatory and the University of Arizona. It combined six individual 1.8-metre (72-inch) mirrors in a circular array on an altazimuth mounting that together had the light-gathering power of a single mirror 4.5 metres (176 inches) in diameter. The cost of construction was very much lower than for the single mirror equivalent at the time. Though such multi-mirror telescopes had been proposed for many years, the concept became a practical reality with the development of the computer control technology necessary to keep each mirror element pointing accurately at the same place in the sky. In 1989, taking into consideration new developments in mirror technology, the decision was made to substitute a single light-weight mirror of 6.5 metres (21 feet) diameter in order to double the light-gathering power and substantially increase the field of view. The conversion was in 1998.