Telescopes from the Ground Up

A multi-mirror telescope is later converted to a single mirror

The Multiple Mirror Telescope (MMT) started out as a pile of spare parts.

Thanks to the conflict between the United States and Russia known as the Cold War, the Air Force had a set of six, lightweight, 72-inch (1.8 m) mirrors that were supposed to have been used in military satellites. They weren’t needed anymore, and the University of Arizona and Smithsonian Institution decided these mirrors would be perfect for the new kind of reflecting telescope they were planning together.

Six of one …

Instead of building one huge mirror, this telescope would use a series of smaller mirrors to equal the light-collecting power of one enormous mirror. It would be like taking six individual telescopes and combining their light to make one image. The MMT would use computers to make sure all the mirrors were always lined up perfectly. It would be the first visible light telescope to use multiple mirrors.

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Multi-mirror Telescopes
Map of Mt. Hopkins, Arizona, USA, where the Multiple Mirror telescope is located.
Image of the Multiple Mirror Telescope with its dome open showing the primary mirror array.Enlarge picture
Multiple Mirror Telescope
Year completed: 1979
Telescope type: Reflector
Light collector: 6 aluminum-coated glass mirrors
Mirror diameter: Each 72 inches
(1.8 m)
Light observed: Visible
Discovery Highlights:
  • Determined that gamma ray bursts — energetic blasts of high-energy radiation — are associated with the explosion of massive stars known as supernovae.