An observatory on Mount Hopkins in Arizona, operated by the Harvard-Smithsonian Center for Astrophysics. The instruments located there, at an altitude of 2,600 metres 8,500 feet, are a 10-metre 32-foot optical reflector for gamma-ray astronomy, 0.61-metre 24-inch and 1.5-metre 60-inch optical telescopes for planetary, stellar and extragalactic astronomy, automatic photoelectric telescopes, and the reconfigured Multiple Mirror Telescope MMT, operated jointly with the University of Arizona for optical and infrared observations. It is named in honour of a former Director of the Smithsonian Astrophysical Observatory who is particularly well known and distinguished for his work on comets.