Observatories of Mauna Kea

May 21, 2001

Part I - The Optical-Infrared Telescopes

The summit of Mauna Kea is considered by many to be the best site for astronomical observations in the world. With approximately 220 clear nights every year, a stable, dry atmosphere which results in sharp images, and no major cities nearby to affect the night sky, it has been chosen as the site for many different telescopes. In this article, we focus our attention on the other facilities which share the mountain with Subaru.

Closest to Subaru on the mountain are the twin domes of the Keck telescopes, operated by the University of California, the California Institute of Technology, and the National Aeronautics and Space Administration (NASA). Each has a diameter of 10 meters, making them the largest fully steerable optical-infrared telescopes in the world. Unlike Subaru and the other telescopes on the mountain, the Keck primary mirrors are constructed not from a single piece of glass, but from 36 separate hexagonal elements, each approximately 2 meters across. The Keck I and Keck II telescopes began their science observations in 1993 and 1996, respectively.

Next comes the 3-meter Infrared Telescope Facility (IRTF), operated on behalf of NASA by the University of Hawai`i. IRTF is intended to provide support for NASA's program to explore the Solar System through coordinated observations with existing or planned missions, or simply by undertaking studies which will provide the intellectual groundwork for future missions. Although Solar System observations are the main priority of IRTF, the telescope performs observations in all areas of astronomy. Infrared observations are important in many areas of astronomical research, ranging from local star forming regions (where they can penetrate the thick veils of dust) to studies of the most distant galaxies (where the Dopper shift caused by the expansion of the Unvierse moves the light to ever longer wavelengths).

Moving along, we come to the 3.6-meter Canada-France-Hawai`i Telescope (CFHT). CFHT celebrated its 21st birthday in August 2000. One of the projects upon which CFHT is embarking in this era of 8-10 meter telescopes is MegaCam, a prime-focus camera which will contain 40 CCDs and provide a field of view of one square degree, four times as large as Suprime-Cam's. It will therefore be able to survey the sky almost as quickly as Suprime-Cam, despite having a primary mirror that gathers only one fifth the light compared to Subaru's.

Up the ridge from CFHT is Gemini North whose primary mirror is 8.1  meters across, only slightly smaller than Subaru's. Gemini North is one of a pair of telescopes funded by an international consortium of the USA, UK, Canada, Australia, Chile, Brazil, and Argentina; the other, Gemini South at Cerro Pachon in Chile, saw First Light in November 2000. Together, these two telescope can observe the entire celestial sphere.

Apart from operating the IRTF and having access to all the telescopes on the summit, the University of Hawai`i (UH) has its own 2.2-meter telescope. Although much smaller than the other telescopes on the island, there are many projects for which a very large telescope is not required; in addition, since there are not as many UH staff to apply for time on the 2.2-meter as there are, for example, Japanese astronomers to apply for time on Subaru, observers can have larger allocations of time which can make up for the smaller light-gathering power of the telescope.

The United Kingdom Infrared Telescope (UKIRT), like the IRTF, is designed solely for performing observations in the infrared part of the spectrum. At 3.8 meters in diameter, it is the largest such telescope in the world and, as a dedicated infrared telescope, it can host instruments which a more versatile telescope such as Subaru cannot. One such instrument is the wide-field camera (WFCAM), currently being build in Edinburgh, UK, which will be able to observe a field of view one degree in diameter. UKIRT is operated by the Joint Astronomy Centre in Hilo, which is supported by the research councils of the United Kingdom, Canada, and the Netherlands.

The smallest telescope on the summit is the University of Hawai`i 0.6-meter telescope. Installed in 1969, it also has the distinction of being the first telescope used for research on Mauna Kea.





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