The Majestic Nicholas U. Mayall 4-meter Telescope

The Nicholas U. Mayall 4-meter Telescope, named for the former Director of Kitt Peak National Observatory (KPNO), was the second-largest telescope by aperture at the time of its first light in 1973. The Mayall telescope currently hosts the Dark Energy Spectroscopic Instrument (DESI), the most powerful multi-object survey spectrograph in the world. DESI's goal is to measure the effect of dark energy on the expansion of the Universe. To this end, it is creating the largest 3D map of the Universe including 40 million galaxies.