title: Keck Observatory
text: The W. M. Keck Observatory is a pair of two large, ground-based telescopes located at Mauna Kea, Hawaii. Sitting four km (more than two miles) above sea level, the paired telescopes are used to examine light from distant stars in great detail. The primary mirrors of each of the two telescopes are 10 meters (33 feet) across, making them slightly smaller than the Gran Telescopio Canarias primary mirrors.
  
  However, all of the light collected by the Keck Observatory primary mirrors (75.76m2) is sent to the secondary mirror and the instruments, compared to GTC's primary mirror, which has an effective light-collection area of 73.4m2, or 25.4 square feet less than each of the Keck Observatory primary mirrors. Because of this fundamental difference in design, Keck Observatory's telescopes arguably remain the largest steerable, optical/infrared telescopes on Earth.
  
  Related pages
   La Silla Observatory
   Very Large Telescope
  
  Other websites 
   W.M. Keck Observatory (official site)
   The Mauna Kea Observatory (official site)
  
  Observatories in the United States
  Buildings and structures in Hawaii