Nicholas U. Mayall Telescope

In 1961, after work had moved forward on other telescopes, Mayall proposed an even larger 150-inch mirror telescope for Kitt Peak. Site construction began in 1968 and by 1971 the mirror was delivered to the site. The mirror was made by Owens-Illinois The telescope was originally designed with three focal point options: the prime focus, a wide-field R/C focus, and a coudé focus. The telescope was dedicated in the summer of 1973, at which time it was the second largest telescope by aperture in the world. The telescope was named after Mayall who was the director of Kitt Peak National Observatory for over a decade. == Instruments ==

Examples of instruments over its lifetime include various spectrographs, Cryogenic Camera, the Phoenix spectrometer, and the DLIRIM. This camera had eight 2048 × 4096 CCD sensors. This prime focus camera was used for a 3-band survey in support of the upcoming DESI instrument. The FTS was used between 1975 and 1995, creating an archive of recorded spectra. It was noted for collecting infrared spectrum before the advent of infrared imaging arrays. Very little is known about dark energy, the supposed pressure responsible for the accelerating expansion rate of the universe. DESI has five thousand fiber optic sensors, each one being robotically targetable at the focal plane. 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. DESI achieved first light in 2019 and was commissioned in March of 2020. Due to the COVID-19 pandemic, full operations have been delayed until mid-2021. == Discoveries & observations ==

by the 4-meter (158 inch) aperture Mayall telescope, a ground-based optical telescope. '' fast Pluto flyby probe in 2015; Plutonian surface shown In 1976 the Mayall Telescope was used to discover methane ice on planet Pluto. The FTS on Mayall was also used to study methane in the outer solar system in the 1980s. The study included observation of monodeutered methane on Titan, a moon of Saturn noted for its thick atmosphere. The observations helped understand the history of that galaxy, which in turn helps understand Earth's galaxy, the Milky Way. ==Contemporaries on commissioning==

The Mayall was the second-largest telescope when inaugurated, between the Hale (5 m) and Shane (3 m). Largest telescopes 1973: Here is the dedication of the telescope with its namesake at the eyepiece: ==Observation examples==

File:DESI_Installed_on_the_Mayall_4-meter_Telescope.jpg|DESI Installed on the Mayall 4-meter Telescope ==See also==