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Name: Nicholas U. Mayall Telescope

Size: 4 meter (158 inches)

Type: Reflecting

First Light: February 27, 1973

Focal Ratio: f/2.7 (Prime)

Mounting: The equatorial mounting has an axis of 32 degrees with a "horseshoe" bearing (right ascension, parallel to earth's axis) and a perpendicular bearing (declination)


  • The building consists of ten hexahedrons, each 96 feet tall and 33 feet wide, weighing 35 tons. The building is 187 feet in height with a floor space measuring 30,000 square feet.
  • The telescope is mounted on a cement pier that is completely separate from the building and the dome. It measures 92 feet above ground and is 37 feet in diameter in the shape of a hollow cylinder.
  • The dome is constructed of 0.25 inch steel plate in a double shell structure. The diameter of the outer shell measures 108 feet, the inner diameter is 102 feet. The dome's interior is covered with 26,600 square feet of embossed aluminum insulating panels. The louvers were added in 1997 for improved air circulation and temperature control. The dome weighs nearly 500 tons and moves with the telescope. The dome is built to withstand winds of 120 mph.

Mirror: The primary mirror has a diameter of 4 meters (158 inches), weighs 15 tons and is fabricated from fused quartz. The mirror is polished to one millionth of an inch. It is coated with reflective aluminum at a thickness of one thousandth of a human hair. The back of the mirror is supported by 33 computer controlled pneumatic pads and the mirror edge is supported by 24 counter balanced push-pull levers.

At 4 meters, the Mayall Telescope is the largest in Kitt Peak National Observatory. That means, it has a primary mirror of greatest diameter. The second largest telescope on the mountain is the WIYN 3.5 Meter.

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NOAO is operated by the Association of Universities for Research in Astronomy (AURA), Inc. under cooperative agreement with the National Science Foundation. The Kitt Peak Virtual Tour is developed and maintained by the NOAO Educational Outreach Office.

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