Nicholas U. Mayall Telescope

Rank in Arizona: #404of 727 ranked
Overall score: Score 38.3 out of 100medium confidence
Category: Observatory

The Nicholas U. Mayall Telescope, also known as the Mayall 4-metre Telescope, is a four-metre (158-inch) reflecting telescope at Kitt Peak National Observatory in Arizona, named after the astronomer Nicholas U. Mayall. It saw first light on 27 February 1973, when it was the second-largest telescope in the world, and was dedicated on 20 June 1973 after Mayall's retirement as director; the initial observers included David Crawford, Nicholas Mayall and Arthur Hoag. Its mirror has an f/2.7 hyperboloidal shape and is made from a two-foot-thick fused quartz disc supported in an advanced-design mirror cell. The prime focus has a field of view of 3.2 degrees, six times that of the Hale reflector. The telescope hosts the Dark Energy Spectroscopic Instrument. An identical instrument, the Víctor M. Blanco Telescope, was later built at the Cerro Tololo Inter-American Observatory in Chile.

Where it is

Nicholas U. Mayall Telescope is a observatory near Altar Valley, in Pima County. It is one of the observatories in this database, and appears in the statewide ranking of Arizona attractions.

How this ranking was reached

No official visitor count is published for Nicholas U. Mayall Telescope, so its score rests on public interest and tourism significance, and is capped below the level a measured attraction can reach. That is why the medium confidence above is not higher. The weighting is explained in full on the methodology page, and every axis is broken out under Facts and sources at the foot of this page.

Note on the data: No official visitor count is published for this attraction.

Mentioned in

Arizona protects its night sky in one set of places and uses it in another — Eight Arizona attractions hold International Dark Sky Park status and all eight publish visitor counts; twelve working observatories publish none.

Sources

Public interest: Wikimedia pageviews (en.wikipedia, human traffic), 2024
Coordinates and designations: Wikidata(opens in a new tab)
County: U.S. Census geography via FCC Area API, resolved from coordinates
Official site: https://noirlab.edu/public/programs/kitt-peak-national-observatory/nicholas-mayall-4m-telescope/(opens in a new tab)

Record last verified 2026-08-12.

More photographs

Montebest, CC BY 3.0 · licence(opens in a new tab) · source(opens in a new tab)
DESI/Fiske Planetarium/LBL, CC BY 4.0 · licence(opens in a new tab) · source(opens in a new tab)

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