Alpine visitor guideWhere the ocean floor ends in starlight

Gemini North is the northern half of the international Gemini Observatory. The 8.1-meter telescope works across optical and infrared wavelengths, often with adaptive optics. Its twin, Gemini South, sits in Chile — together they cover the whole sky. In the photo, Gemini North is second from the left: the silver, flat-topped dome between CFHT (far left) and UKIRT, with the UH 2.2-meter farther downslope on the right.

Built by an international partnership (including the United States, Canada, Chile, Argentina, Brazil, and others over the project’s history) and operated today through NOIRLab, Gemini North reached first light in 1999. The enclosure is designed to cool quickly, so the air inside matches the cold night air outside and doesn’t blur the view.

Science programs span exoplanets, stellar populations, supernovae, and distant galaxies. Laser-guide-star adaptive optics and infrared instruments let it resolve fine structure that would otherwise be blurred by the atmosphere. Visitors see the distinctive silver dome from the summit road; like neighboring facilities, it is a research telescope, not a public tour stop.

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Keck I and Keck II each use a 10-meter segmented primary mirror. Together they remain among the most productive optical–infrared telescopes on Earth, supporting everything from exoplanet studies to distant galaxies. The twin domes are a landmark on the summit ridge — visible from the road and the best public option among summit facilities.

The Keck Visitor Gallery is open to the public (Keck lists daily hours around 10 a.m.–2:30 p.m. — confirm before you go). Look for the blue door / viewing area for Keck I, with exhibits and restrooms. It is a controlled gallery, not a free roam of the whole facility.

Funded by the W. M. Keck Foundation and operated by the California Association for Research in Astronomy (Caltech and the University of California), with NASA as a partner, Keck I saw first light in 1993 and Keck II in 1996. Each primary mirror is built from 36 hexagonal mirror segments working as one 10-meter surface — a design that made large apertures practical before today’s giant monolithic blanks.

Both telescopes use adaptive optics to sharpen images through the atmosphere, and they can work together as an interferometer. Decades of programs have included exoplanet atmospheres, black-hole masses in galactic nuclei, and some of the most distant galaxies and quasars ever studied. The twin silver domes are among the easiest landmarks to spot from the summit road.

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UKIRT was a workhorse infrared telescope on Maunakea from 1979 until science operations ended on September 15, 2026. The University of Hawaiʻi announced the closure as part of reducing the number of telescopes on the mountain; UKIRT is the third Maunakea facility to enter decommissioning (after CSO and Hōkū Keʻa). Removal is currently planned for completion by about 2030.

Built by the UK Science Research Council and opened in 1979, UKIRT was among the first large telescopes optimized for infrared work on Maunakea. For decades it was operated through the Joint Astronomy Centre; later stewardship included the University of Hawaiʻi and partners, with long-running science support from the U.S. Naval Observatory. Aging facilities, funding limits, and UH Master Plan / lease obligations led to ending science operations.

Infrared surveys and instruments from UKIRT mapped the near-infrared sky at a scale few facilities could match, feeding catalogs used for brown dwarfs, star clusters, and distant galaxies. The white cylindrical enclosure with its smooth dome sits just east of Gemini North on the summit ridge — third from the left in the four-telescope Gemini photo. Visitors still see the building from the road while decommissioning planning proceeds; it is not a public tour stop.

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The JCMT is the largest single-dish telescope on Maunakea. Its 15-meter dish observes at submillimeter wavelengths — light between infrared and radio — to map cold molecular clouds where stars and planets form. Visitors see the white weather enclosure near the west side of the summit ridge; the facility itself is not open for public tours.

Built as a UK–Canada–Netherlands partnership and opened in 1987 (dedicated by Prince Philip), the telescope was designed for the dry air above Maunakea so it can work through the narrow submillimeter “windows” blocked by water vapor at lower elevations. Since 2015 it has been operated by the East Asian Observatory, with partners in China, Japan, South Korea, and Taiwan.

Its cameras made the facility famous. SCUBA (1990s) and later SCUBA-2 (from 2011) image cold dust that optical telescopes miss — from nearby star-forming clouds to distant, dust-obscured galaxies. The dish has also joined global millimeter networks, including the Event Horizon Telescope collaboration that produced the first image of a black hole.

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Subaru is operated by the National Astronomical Observatory of Japan. Its 8.2-meter primary is one of the largest monolithic mirrors ever made for astronomy. Wide-field cameras and adaptive optics let it survey large stretches of sky from the dry, stable air above Maunakea.

Construction was led by Japan’s National Astronomical Observatory (NAOJ); the telescope reached first light in 1998 and began regular science in 1999. “Subaru” is the Japanese name for the Pleiades. The primary is a single piece of glass — one of the largest monolithic mirrors ever figured for astronomy — housed in an open-style enclosure designed to keep the air inside as stable as the site outside.

Signature instruments include wide-field cameras such as Suprime-Cam and later Hyper Suprime-Cam, which map huge patches of sky for surveys of galaxies, dark matter, and transient objects. Adaptive-optics systems and infrared instruments add high-resolution work on planets, stars, and galactic nuclei. The cylindrical silver enclosure is a clear landmark on the east side of the summit complex.

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CFHT is known for wide-field imaging — surveying huge patches of sky in a single exposure. The 3.6-meter telescope is a partnership of Canada, France, and the University of Hawaiʻi, and it remains one of the most recognizable domes on the ridge.

The partnership of Canada, France, and the University of Hawaiʻi dedicated the telescope in 1979. Its 3.6-meter primary and classical equatorial mount made it one of the early “large” optical telescopes on the mountain, and the bright white dome remains a landmark on the northwest end of the ridge.

Modern instruments such as MegaCam turned CFHT into a survey powerhouse: wide-field imaging programs have measured weak gravitational lensing, mapped large-scale structure, and discovered distant solar-system bodies. Spectrographs and adaptive-optics work continue alongside those surveys. In the Gemini ridge photo, CFHT is the leftmost of the four domes.

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Often called the UH88, this 2.2-meter telescope helped establish Maunakea as a world-class site. It continues as a University of Hawaiʻi research and training instrument, smaller than the giants nearby but historically important.

The University of Hawaiʻi 2.2-meter (often nicknamed the UH88) saw first light in 1970 — among the earliest research telescopes on the summit. Its success helped prove that Maunakea’s altitude, dryness, and stable air could support world-class optical astronomy and paved the way for the larger international facilities that followed.

Today it remains a University of Hawaiʻi research and training telescope: graduate students and faculty use it for imaging and spectroscopy while larger neighbors handle the deepest surveys. In the Gemini ridge photo it is the rightmost of the four domes, sitting a bit farther downslope than CFHT, Gemini, and UKIRT.

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NASA’s IRTF is optimized for infrared observations of planets, moons, asteroids, and other solar-system targets, as well as cooler stars and dust. The 3-meter telescope has supported decades of planetary astronomy from Maunakea.

NASA funded the facility; the University of Hawaiʻi Institute for Astronomy operates it under contract. First light was in 1979. The 3-meter primary and infrared-optimized instruments make it especially useful for bright, extended solar-system targets that benefit from continuous monitoring rather than the largest apertures.

Programs routinely observe Jupiter and Saturn’s atmospheres, icy moons, asteroids, comets, and transient events such as impacts or outbursts. Ground-based infrared spectroscopy from IRTF often complements spacecraft flybys and orbiters. The compact white dome sits among the lower-summit cluster of mid-size telescopes along the access road.

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The SMA is an interferometer: multiple movable 6-meter antennas combine signals to act like a much larger telescope. It sits on the west side of the ridge near Puʻupoliʻahu and studies cold gas, dust, and planet-forming disks at submillimeter wavelengths.

The array is a partnership led by the Smithsonian Astrophysical Observatory with Academia Sinica (Taiwan) and other collaborators. Science operations began in the early 2000s. Eight 6-meter antennas can be repositioned on concrete pads so baselines change from compact to extended configurations, trading field of view for finer angular resolution.

Observers use it to map molecular line emission and continuum dust in planet-forming disks, star-forming cores, and active galactic nuclei. The SMA also participates in very-long-baseline networks that link Maunakea with other millimeter arrays. From the road you see the cluster of white dishes west of the main ridge, near Puʻupoliʻahu — stay on designated routes and do not walk among the pads.

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Puʻupoliʻahu is a cinder cone on the western side of the summit area, associated in Hawaiian tradition with Poliʻahu, goddess of snow. It is a cultural and landscape landmark, not a telescope. In the photo it is the large red cone on the right; the buildings in front of it are, from left to right, the James Clerk Maxwell Telescope (JCMT), the Submillimeter Array’s maintenance and control building, and three SMA antennas. Stay on roads and marked areas; do not climb culturally sensitive puʻu.

In Hawaiian tradition, Poliʻahu is associated with snow and the high, cold places of Maunakea; the puʻu that bears her name is part of a sacred landscape that includes other named cones and the summit area itself. Cultural protocols ask visitors to treat these places with respect — no climbing sensitive puʻu, no leaving offerings that litter the ground, and no treating the slopes as a playground.

Geologically it is a volcanic cinder cone on the western side of the summit complex, near the Submillimeter Array pads. Summit maps often label it to help drivers get their bearings. Stay on roads and marked areas, and follow current Maunakea access rules.