Nicholas U. Mayall Telescope

Under the dome

Examples of instruments over its lifetime include various spectrographs, Cryogenic Camera, the Phoenix spectrometer, and the DLIRIM.[6]

The KNPO Mosaic camera was installed in 1998, and was designed for the prime focus.[9] This camera had eight 2048 × 4096 CCD sensors.[9] This lead to another camera Mosaic II for the CTIO 4-m telescope in the southern hemisphere.[9]

Mosaic3

Mosaic3 was an imaging camera for the Mayall telescope.[10] This prime focus camera was used for a 3-band survey in support of the upcoming DESI instrument.[10]

Fourier Transform Spectrograph

One instrument used with telescope was the Fourier Transform Spectrograph.[11] The FTS was used between 1975 and 1995, creating an archive of recorded spectra.[12] It was noted for collecting infrared spectrum before the advent of infrared imaging arrays.[12]

Over the time of its operation 10,000 spectra were taken of 800 different astronomical targets, and these were made available in the SpArc data archive in the early 21st century.[12]

DESI

In late 2019 the DESI instruments was nearing completion, an instrument designed to help understand dark matter.[13] Dark Matter was theorized by Fritz Zwicky in 1933, based on calculations of star motion that seemed to require more mass — dark matter.[13] Zwicky used then largest telescope in the world, the 100-inch (254 cm) Hooker telescope in California for this research.[14]

DESI has five thousand fiber optic sensors, each one being robotically targetable at the focal plane.[13][15] Planned to examine the nature of millions of galaxies and quasars, the instrument has been a decade in construction and features contributions from hundreds of researchers.[13]

The telescope control software was also upgraded in the 2010s to prepare for DESI.[16]

In October 2019, DESI achieved its first light test and in March was commissioned. Full operations were expected by the end of 2020.[17]

Image of Abell 30 by the 4-meter (158 inch) aperture Mayall telescope, a ground-based optical telescope.

Methane ice was confirmed by New Horizons fast Pluto flyby probe in 2015; Plutonian surface shown

In 1976 the Mayall Telescope was used to discover methane ice on planet Pluto.[18]

The FTS on Mayall was also used to study methane in the outer solar system in the 1980s.[19] The study included observation of monodeutered methane on Titan, a moon of Saturn noted for its thick atmosphere.[19] The Mayall was also one of several large telescopes that was part of a study of the Andromeda galaxy.[20] The observations helped understand the history of that Galaxy, which turn helps understand Earth's galaxy, the Milky Way.[20]

The Mayall was the second-largest telescope when inaugurated, between the Hale (5 m) and Shane (3 m).

Largest telescopes 1973:

#	Name / Observatory	Image	Aperture	Altitude	First Light	Special advocate
1	Hale Telescope Palomar Obs.		200 inch 508 cm	1713 m (5620 ft)	1949	George Ellery Hale
2	Mayall Telescope Kitt Peak National Obs.		158 inch 401 cm	2120 m (6955 ft)	1973	Nicholas Mayall
3	Shane Telescope Lick Observatory		120 inch 305 cm	1283 m (4209 ft)	1959	Nicholas Mayall C. Donald Shane
4	Harlan J. Smith Telescope McDonald Observatory		107 in 270 cm	2070 m (6791 ft)	1968	Harlan J. Smith

Here is the dedication of the telescope with its namesake at the eyepiece:

Mayall on March 2, 1973 viewing through the telescope to be named in his honor.

• List of astronomical observatories
• List of largest optical reflecting telescopes
• List of largest optical telescopes in the 20th century
• List of the largest optical telescopes in the contiguous United States

• Media related to Nicholas U. Mayall Telescope at Wikimedia Commons
• The Mayall 4-meter Telescope - official site.
• Scale model of 4 meter
• Active Optics Upgrade