At 13,796 feet, the summit of Mauna Kea on the Big Island of Hawaii houses the world's largest observatory for optical, infrared, and sub-millimeter astronomy. Because of the extreme altitude here, astronomers and technicians must acclimatize and live at an intermediate altitude, so living facilities were constructed in 1982 at a lower elevation, 9,300 feet, at the Onizuka Center for International Astronomy, informally known as the Onizuka Astronomy Complex.
As an astronomy site, Mauna Kea is almost perfect. The mountain atmosphere is extremely dry and cloud-free. The area's proportion of clear nights ranks among the highest in the world. Also, a tropical inversion cloud layer exists at 2,000 feet, insulating the upper atmosphere from moist maritime air, city lights, and atmospheric pollutants.
The community at the Onizuka Astronomy Complex is truly international. The 13 research telescopes atop Mauna Kea are operated by representatives of nearly a dozen countries, including Argentina, Australia, Brazil, Canada, Chile, France, Japan, the Netherlands, Taiwan, the United Kingdom, and the United States.
A number of universities and private institutions are also represented. They include Caltech, the University of California, the University of Hawaii, the Smithsonian Astrophysical Observatory, and the National Aeronautics and Space Administration (NASA), among others.
Nine of telescopes atop Mauna Kea are intended for optical and infrared astronomy. Three others are used for sub-millimeter wavelength astronomy, and there is one dedicated to radio astronomy. Caltech's two Keck models are the largest optical/infrared telescopes in the world, each with a mirror diameter of 10 meters.
The very first telescope set up here was the University of Hawaii's 0.6-meter version for educational use in 1968. The most recent addition is the Smithsonian's 8x6-meter sub-millimeter array, completed in 2002.
The Hale Pohaku (Hawaiian for "stone house'') of the Onizuka Astronomy Complex can accommodate up to 72 people working at the summit. There is also a visitor center, which is open to the public year round, and a number of support buildings for maintenance, storage and meetings.
At the Visitor Information Station (VIS), nightly stargazing tours have been organized between 6pm and 10pm. A solar telescope with protective filters has been set up for daytime viewing. The VIS also operates weekend tours to the summit, where visitors can peer through the huge telescopes and observe the heavens.
Other features of the Onizuka Astronomy Complex include a bookstore, public restrooms, and a sundries shop. Hot water and a microwave oven are also provided for use by visitors. However, there are no gas stations closer than 30 miles, so those coming to the complex by car are advised to fuel up before setting out for a visit.
The Onizuka Astronomy Complex is about an hour's drive from Hilo. Drivers should take the Puainako Extension to Saddle Road (State Highway 200) and then turn right, just before mile marker #28, onto "Mauna Kea Access Road.'' Six miles along, the VIS can be seen on the right side of the road.