Can You Look Through a Telescope on Mauna Kea?

No. You cannot look through any of the giant research telescopes on Mauna Kea’s summit. Keck, Subaru, Gemini and their neighbors have no eyepieces at all: their light ends at electronic detectors and spectrographs, and most of the astronomers using them are not even on the mountain. They observe remotely from Waimea, Hilo or the mainland.

You can still look through a real telescope in Hawaii, just not a research one. Guided Mauna Kea tours set up 11-inch Celestron telescopes at mid-mountain after sunset, the Visitor Information Station runs a free monthly telescope night by reservation, and on Maui, Haleakalā National Park holds free ranger star programs with telescope viewing. For most visitors, the best eyepiece experience is a tour telescope showing Saturn’s rings and Jupiter’s moons. The Keck Visitors’ Gallery adds something different: a daytime look at a real 10-meter telescope through a viewing window.

The most-booked way to do both halves of the evening, sunset at the summit among the domes and then an eyepiece session lower down, is the tour below. Check dates and the live price here.

Five Things to Know Before You Go

1. Research telescopes have no eyepieces because the human eye is a poor detector. The eye registers only about 1 to 5% of the light that reaches it and cannot build up an image for longer than about a tenth of a second. Modern CCD and CMOS detectors register upwards of 90% of incoming photons and can collect light for hours. Together, that makes a modern camera thousands of times more sensitive than the eye, so no professional would put an eyepiece on a 10-meter mirror.
2. Most Mauna Kea observing is now remote, and much of it is spectroscopy, not pretty pictures. At Keck, all observing is done remotely from the Waimea headquarters or approved remote sites, with only a small support crew at the summit. Astronomers split light into spectra to measure what a star is made of, how hot it is and how it moves, and magnification plays no part in that work.
3. The real eyepiece options in Hawaii are tour telescopes, the VIS monthly event, resort and beach programs, and Haleakalā’s ranger programs. All of them use amateur-class instruments, roughly 8 to 12 inches across, which show the planets, the Moon and the brighter deep-sky objects well.
4. Smart telescopes have quietly changed backyard astronomy. Devices like the ZWO Seestar and Vaonis Vespera have no eyepiece either. They stack many short exposures, the same photon-counting logic the professionals use, at consumer prices, and several Big Island tour operators now use them to send you deep-sky photos.
5. You can control real research-grade telescopes online, free or cheaply, through Las Cumbres Observatory, Harvard’s MicroObservatory and the LCO-operated Faulkes Telescope North on Haleakalā.

Other Experiences You Might Enjoy

A telescope evening fits easily into a wider Big Island trip. Many visitors add ʻImiloa Astronomy Center in Hilo for the planetarium, a day at Hawaiʻi Volcanoes National Park for the Kīlauea crater, a Native Hawaiian-guided hike on the lower Humuʻula Trail, or a Kona-side sunset-and-stars tour with photos. Tours and tickets around the island:

Why the Research Telescopes Have No Eyepieces

For most of astronomy’s history, observing meant a human eye at an eyepiece. That era ended in stages. In the late 19th and early 20th centuries, photographic plates replaced the eye, because a plate could gather light over a long exposure and keep a permanent record, even though early emulsions registered only around 1% of the photons that reached them. From the 1970s and 80s the charge-coupled device (CCD) replaced film, and more recently CMOS detectors have joined it.

Three numbers explain why no serious research telescope has an eyepiece today:

• Quantum efficiency. Quantum efficiency (QE) is the share of arriving photons a detector registers. The human eye’s effective QE is only around 1 to 5%. A photographic plate managed roughly 1%. A modern astronomical CCD or CMOS sensor reaches 90% or more, recording almost every photon that lands on it.
• Integration time. The eye refreshes roughly every tenth of a second and cannot build up a faint image over time. A detector can integrate, or collect, light for minutes or hours in a single exposure, and then many exposures can be combined. This is the biggest advantage of all: a faint galaxy that sends only a trickle of photons each second becomes detectable if you keep counting for an hour. No amount of staring through an eyepiece can do that.
• Linearity and data. A CCD responds in direct proportion to the light it receives, to 0.1% or better, so its output is a scientific measurement as well as a picture. It is also digital, so it can be calibrated, archived and analyzed by anyone, anywhere.

There is a second, deeper reason. Most modern observing is spectroscopy, not imaging. When astronomers split starlight into its spectrum with a spectrograph, they measure exactly which wavelengths a star emits or absorbs, which reveals its chemical makeup, its temperature, its motion (through the Doppler shift) and more. In this mode there is no image to magnify. As the American Museum of Natural History’s education materials put it, “no image of the star is even created, so there is nothing to magnify.”

Finally, many Mauna Kea instruments detect light your eye cannot perceive at all. Infrared and submillimeter wavelengths are invisible to people, so an eyepiece on the James Clerk Maxwell Telescope, which observes at wavelengths of 0.4 to 1.4 mm, would show you nothing. At Keck or Subaru the light path ends at an instrument, a camera or spectrograph the size of a car or a small room. There is physically nothing to look through.

How Observing Works on Mauna Kea Today

If you picture astronomers shivering at the summit with an eye to the telescope all night, the reality is very different.

• Remote observing. The W. M. Keck Observatory pioneered remote observing on Mauna Kea, and today all Keck observing is done remotely, mainly from the observatory’s headquarters in Waimea, about 32 km away and at 2,700 ft instead of 13,796 ft, where a brain short of oxygen makes mistakes, or from roughly 15 approved remote sites on the mainland and elsewhere. Keck’s own site says: “Observing from the summit is no longer supported.” On a typical night, a crew of two at the telescope handles any problems. Summit operations in general run lean; UKIRT, for example, was down to eight full-time staff in its final year.
• Who does what. At the summit, an observing assistant (the telescope operator) runs the telescope and, on adaptive-optics nights, the AO system. The astronomer, often in Waimea or on the mainland, runs the science instrument and decides what to observe, with help from staff astronomers.
• Queue and classical observing. In classical observing, an astronomer is assigned particular nights. In queue (or service) observing, staff work through a ranked list of programs, each run when the conditions best suit it, which is ideal for follow-up work on objects that change. Gemini North relies heavily on queue scheduling and built its identity around rapid follow-up of new events; Keck keeps more classical observing. The exact split varies by observatory and semester, and no single figure is published.
• Adaptive optics and laser guide stars. Earth’s atmosphere blurs starlight. Adaptive optics (AO) measures that blurring and corrects it with a deformable mirror that changes shape about 1,000 times a second. To measure the distortion you need a bright reference star nearby, but bright stars sit close to only about 1% of the sky. The answer is the laser guide star: a laser tuned to the sodium wavelength of 589 nm, run at around 14 W, excites atoms in a natural layer of sodium about 90 to 95 km up and creates an artificial star wherever the telescope points. That orange beam is what visitors sometimes see rising from the summit at night. Keck II was the first large telescope to correct its images with a laser guide star, in 2003.
• From photons to paper. Detected photons become calibrated data through a reduction pipeline, which removes the instrument’s own signature and calibrates wavelength and brightness. Then comes analysis, and then a peer-reviewed paper, often months or years after the night itself.

What Each Mauna Kea Telescope Does

Keck I and Keck II. Twin 10-meter telescopes whose mirrors are each made of 36 hexagonal segments, the telescopes that pioneered that design. Their instruments include HIRES (the High Resolution Echelle Spectrometer, used heavily for finding exoplanets by the “wobble” they cause in their stars), NIRSPEC (a near-infrared spectrograph), KCWI (the Keck Cosmic Web Imager) and the AO-fed cameras NIRC2 and OSIRIS. Keck’s best-known result is the 2020 Nobel Prize in Physics awarded in part to Andrea Ghez, who used Keck’s adaptive optics and infrared cameras (NIRC, NIRC2 and OSIRIS) to track stars orbiting the supermassive black hole at the center of the Milky Way, Sagittarius A*, over more than 25 years.

Subaru. An 8.2-meter telescope run by the National Astronomical Observatory of Japan (NAOJ), unusual for its wide-field instruments at prime focus. Hyper Suprime-Cam is an 870-megapixel camera with 116 CCDs and a 1.5° field, able to photograph an area of sky as large as nine full Moons in a single exposure; it is the camera behind the Subaru Strategic Program’s survey of dark matter and the distant universe. The Prime Focus Spectrograph (PFS) places 2,400 movable optical fibers across a field about 1.3° wide to take that many spectra at once. PFS began science operations in February 2025, a flagship of what NAOJ calls the “Subaru Telescope 2.0” era.

Gemini North. An 8.1-meter telescope, part of the international Gemini partnership run through NSF NOIRLab, known for flexible queue scheduling and quick follow-up of events in the sky. Its instruments include GMOS (the Gemini Multi-Object Spectrograph) and GNIRS (the Gemini Near-Infrared Spectrograph, covering 0.8 to 5.4 μm). Gemini is a workhorse for following up supernovae and other short-lived events, and increasingly the alerts coming from the Vera C. Rubin Observatory.

CFHT (Canada-France-Hawaii Telescope). A 3.6-meter telescope whose MegaCam wide-field imager helped find some of the most distant quasars known, including one at a redshift of 6.43, and whose SPIRou near-infrared spectropolarimeter searches for planets around cool stars.

IRTF (NASA Infrared Telescope Facility). A 3-meter-class infrared telescope (its primary mirror is 3.2 m across, with an effective aperture of 3.0 m) run by the University of Hawaiʻi Institute for Astronomy for NASA. At least half of its observing time is reserved for planetary science, and it is NASA’s main ground-based telescope for studying planetary atmospheres, comets and near-Earth objects. Its workhorse instrument is SpeX, an infrared spectrograph covering 0.7 to 5.4 μm. IRTF spectroscopy, which identified nitrogen and carbon monoxide ice on Pluto, helped choose the hemisphere New Horizons studied in its 2015 flyby, and the telescope has supported missions from Juno to Japan’s Akatsuki. It, too, is run largely by remote observing.

JCMT and the Submillimeter Array. The James Clerk Maxwell Telescope is a 15-meter dish, the largest single-dish submillimeter telescope in the world, run by the East Asian Observatory. Its SCUBA-2 camera picks up the faint heat glow of cold dust between the stars, mapping where new stars are forming. The Submillimeter Array (SMA) links eight 6-meter antennas as one interferometer and is run jointly by the Smithsonian Astrophysical Observatory and Taiwan’s Academia Sinica. JCMT and the SMA were the two Mauna Kea stations in the Event Horizon Telescope, which produced the first image of a black hole (M87*, given the Hawaiian name Pōwehi, released in 2019) and the image of the Milky Way’s own black hole, Sagittarius A*, released in 2022.

UKIRT (United Kingdom Infrared Telescope). A 3.8-meter infrared telescope that opened in 1979 and, in the words of Institute for Astronomy director Doug Simons, “has been one of the most prolific telescopes on the planet.” Its science operations ended on September 15, 2026, as the University of Hawaiʻi announced in July 2026. UKIRT is the third Mauna Kea telescope to be decommissioned, after the Caltech Submillimeter Observatory and Hōkū Keʻa, both removed in 2024, and its removal is due to be finished by 2030. Our observatories guide lists every telescope still standing.

Where You Can Look Through a Telescope in Hawaii

Here is the good news the giant domes cannot give you: there are several real eyepiece experiences.

Big Island summit tours. The permitted Mauna Kea tour companies all carry portable telescopes for a star show after sunset. It is held at mid-mountain, around 9,000 ft, not at the summit, because the summit closes to visitors 30 minutes after sunset and because your night vision works better with more oxygen. The standard instrument is an 11-inch Celestron Schmidt-Cassegrain; Hawaiʻi Forest & Trail and Mauna Kea Summit Adventures both use the CPC 1100 model. On a clear night these show Saturn’s rings, Jupiter’s four Galilean moons, the Andromeda Galaxy and the Moon’s craters in detail. Some operators pair the eyepiece telescope with a smart telescope, a Vaonis Stellina or a Celestron Origin, that photographs deep-sky objects and emails you the images afterwards. Hawaiʻi Forest & Trail’s Mauna Kea Summit, Dinner & Private Star Show ($345, 4.8 stars from 19 GetYourGuide reviews, a thin count on the platform) is the one with both. Almost every summit tour has the same rule: no children under 13, because of the altitude. Our operator comparison lists which telescope each company carries.

The Visitor Information Station’s monthly telescope night. The VIS ended its old nightly telescope program in 2019 because of overcrowding and damage to the site, and there are no public telescopes there on a normal evening. Instead, it runs a free telescope viewing event, by reservation only, roughly once a month: staff take a small group to a site away from the crowds and set up telescopes for about two hours. Places are limited and go quickly, so reserve online well ahead. The VIS itself is open 9 a.m. to 9 p.m. daily, and staff still point out constellations to the naked eye in the evening, weather and staffing permitting. Our Visitor Information Station guide explains how the booking works.

Lower-elevation stargazing and resort programs. Several Big Island operators run stargazing well below the summit, some from dark sites on the Hilo side with a 10-inch Dobsonian, premium eyepieces and nebula filters, and many Kohala Coast and Kona resorts host evening stargazing on the lawn or the beach. These are open to all ages and involve no summit drive. KapohoKine’s Stellar Explorer from Hilo ($189, 4.5 stars from 81 reviews) takes all ages and stargazes on the mountain’s lower slopes; our guide to stargazing beyond the summit covers the rest, including which resort programs are still running.

ʻImiloa Astronomy Center, Hilo. ʻImiloa is a planetarium and science center, so you will not look through a research telescope there, but its full-dome planetarium and exhibits are the best indoor astronomy experience on the island, and they suit families.

On Maui: Haleakalā’s ranger programs. Haleakalā National Park runs free ranger-led night sky programs every week: a 30 to 45-minute talk, with a green laser tracing the constellations, followed by 30 to 45 minutes of telescope viewing when conditions allow. They are held beside the Haleakalā Visitor Center at 9,740 ft. Separately, commercial operators such as Maui Stargazing run tours inside the park with large portable Dobsonians of up to 12 inches. Our Mauna Kea vs Haleakalā comparison sets the two mountains side by side.

Telescope rental is not really a consumer offer in Hawaii. In practice, the rental is a guided tour, where the telescope and an expert come together.

Seeing a Telescope Is Not Looking Through One: Keck and Subaru

At the Keck Visitors’ Gallery, open daily from 10:00 a.m. to 2:30 p.m., you step inside the facility and look through a viewing window, behind a blue door, into the Keck I dome, where you can see one of the twin 10-meter telescopes itself: the segmented mirror, the huge mount and the instrument packages. There are gallery exhibits and public restrooms too. It is a daytime visit, and the telescope is not working while you are there, so you are not looking through it. You are, though, standing a few feet from a machine that produced Nobel Prize-winning science.

Subaru no longer offers public tours. NAOJ officially ended its summit facility tour program on December 15, 2022, after a long suspension, and says there is “no plan to resume it.” You can still see Subaru’s distinctive cylindrical dome from outside, but you cannot go in.

So the honest visitor experience at the summit is this: you see the domes and, at Keck, one telescope through a window, and you do not look through any of them.

Amateur Telescopes: A Buyer’s and User’s Guide

If the summit gives you the bug, here is what actually delivers at home.

For what you can see, aperture matters most. Light-gathering power grows with the square of the aperture (more on that in the next section), but the kind of target matters too:

• Planets and the Moon reward good optics and steady air more than sheer size. Even a 4 to 6-inch telescope shows Saturn’s rings, Jupiter’s cloud belts and lunar detail beautifully.
• Deep-sky objects such as galaxies and nebulae are faint and spread out. Here aperture wins, and an 8 to 12-inch reflector shows far more than a small telescope.

The main telescope types:

• Refractors (lenses): sharp, low-maintenance and excellent on the planets and the Moon, but expensive per inch of aperture, so they are usually small.
• Newtonian reflectors (mirrors): the most aperture for the money, though the mirrors need occasional alignment (collimation).
• Dobsonians: Newtonians on a simple, stable mount, the best value in raw aperture and a superb choice for visual observing.
• Schmidt-Cassegrains (SCTs): compact, computerized and versatile. The 8-inch and 11-inch SCTs are the classic all-rounders, and the 11-inch is exactly what many tour operators carry.

What a beginner can expect. A 6-inch telescope shows the Moon, the planets and the brighter Messier objects well. An 8-inch is the widely recommended first serious telescope. An 11-inch, like the tour operators’ instruments, pulls in fainter galaxies and more detail in globular clusters, but it is heavier and more expensive. Through any eyepiece, galaxies look like faint grey smudges, nothing like the colorful Hubble images. That is normal, and it is exactly why smart telescopes exist.

Smart telescopes are the biggest recent change. These eyepiece-free devices point themselves, stack many short exposures automatically and send a color image to your phone within minutes, professional logic in a consumer box. Approximate US prices, as reported by retailers and reviewers in late 2025 and 2026:

• ZWO Seestar S30: about $349 to $399, an ultra-portable 30 mm model.
• ZWO Seestar S50: about $499, 50 mm, the best-selling budget all-rounder (a Seestar S50 Pro was reported as due later in 2026).
• Dwarflab Dwarf 3: about $549 to $599, with a high-resolution 8.3-megapixel camera.
• Vaonis Vespera II: about $1,590; the Vespera II-X about $2,290; the Vespera Pro about $2,799.
• Celestron Origin: a premium 6-inch system built around a RASA (Rowe-Ackermann Schmidt astrograph) optical design, about $3,999, with a Mark II successor reported at around $4,299.
• Vaonis Stellina: the original premium model, about $3,999 new, now discontinued and harder to find.

Smart telescopes are superb for deep-sky imaging and for showing groups the sky, and they are mediocre to poor on the planets, because their apertures are small and there is no eyepiece. They give you images; the thrill of live photons reaching your eye is a different experience. For that, a traditional Dobsonian still wins.

Binoculars are the underrated first instrument. A pair of 7×50 or 10×50 binoculars shows the Moon, Jupiter’s moons, star clusters, the star clouds of the Milky Way and comets, for a fraction of a telescope’s price and with no setup at all. Most experienced observers say to start here.

Should you bring equipment to Hawaii? For most visitors, no. A smart telescope or compact binoculars travel well, but a serious Dobsonian does not, and a guided tour already provides the telescope. Bring binoculars and leave the big glass at home.

Aperture and Magnification: The Physics in Brief

Two ideas clear up most of the confusion.

Light-gathering power grows with the square of the aperture. Double the aperture and you collect four times the light. Keck’s 10-meter mirror has roughly a million times the collecting area of a dark-adapted human pupil, about 7 mm across, which is why it detects objects billions of times fainter than the eye can see.

Resolving power improves with aperture too. The finest detail a telescope can separate is set by diffraction, and there are two common rules of thumb:

• Dawes limit: resolution in arcseconds ≈ 116 ÷ aperture in mm.
• Rayleigh limit: ≈ 138 ÷ aperture in mm.

So a 100 mm telescope resolves about 1.2 arcseconds, and an 8-inch (200 mm) about 0.58 arcseconds.

Magnification, though, is limited by the air, not the optics. Atmospheric turbulence, which astronomers call “seeing”, usually blurs ground-based images to 1 to 2 arcseconds even at good sites, so pushing the magnification beyond what the air supports gives you only a bigger, blurrier image. The usual guide to the maximum useful magnification is about twice the aperture in millimeters (50× per inch): an 8-inch telescope tops out near 400×, but on an average night the seeing limits useful power to closer to 200×.

That is the key to the giants on Mauna Kea: they are not about magnification at all. They exist to collect photons, to detect the faintest and most distant objects, and, with adaptive optics, to resolve fine detail. Mauna Kea’s value lies in its exceptionally steady, dry, dark air, among the best natural seeing in the Northern Hemisphere, which is why the big telescopes were built there.

Visiting Virtually and Observing Online

You do not need to be on the mountain to get close to these telescopes.

• Keck’s 360° virtual tour. Keck offers an online 360-degree tour of its telescope facility and recommends it “in lieu of a summit visit” to cut traffic on the mountain.
• Subaru’s 3D virtual tour. NAOJ built a 3D walk-through of the Subaru dome interior, released in 2022, that you can explore in a browser or in VR, precisely because in-person tours ended.
• Live webcams stream the summit and the sky, including Subaru’s night-sky camera.
• Telescope networks you can request time on let you take real data yourself:
  • Las Cumbres Observatory (LCO) runs a global network of robotic telescopes, two 2-meter, thirteen 1-meter and ten 0.4-meter, and gives about 1,500 hours a year to educational “Global Sky Partners”. Members of participating programs request observations online.
  • MicroObservatory, run by Harvard and the Smithsonian, is free and open to the public: anyone can request an image from its robotic telescopes online.
  • Faulkes Telescope North, a 2-meter LCO telescope on Haleakalā, is used for education. Schools have historically registered, trained and booked observing slots online. The original Faulkes Telescope Project branding appears to have wound down, although the telescope itself remains in the LCO network, so check the current LCO and Schools’ Observatory routes before relying on it.
• Citizen science projects, for example on Zooniverse, let anyone classify real professional data, including data from Mauna Kea observatories.

What Each Kind of Visitor Should Do

• A child who wants to look through a big telescope. They cannot look through the research telescopes, and under-13s cannot go on summit tours. The better options are a resort or lower-elevation stargazing program (all ages), the VIS monthly event, or ʻImiloa’s planetarium. On Maui, Haleakalā’s ranger programs suit families.
• An amateur astronomer. You will enjoy the Keck Gallery for a close look at a 10-meter telescope, but bring nothing heavy. Book a tour for the 11-inch eyepiece views, or bring a smart telescope or binoculars for the extraordinary dark sky. The science story, adaptive optics, spectroscopy and the Event Horizon Telescope, is the real draw.
• A first-time visitor. A guided summit sunset-and-stargazing tour is the best single package: sunset above the clouds, then real eyepiece views of Saturn and Jupiter at mid-mountain. The Mauna Kea Summit Sunset & Stargazing Tour ($289, 4.8 stars from 759 reviews) is the most-booked; Arnott’s Hilo: Mauna Kea Summit Tour at Sunset ($255, 4.8 stars from 54 reviews, capped at 13 guests) costs less.
• An astronomy student. Combine the Keck Gallery, ʻImiloa and hands-on remote observing through LCO or MicroObservatory. Understanding remote and queue observing and spectroscopy is worth more than any eyepiece.
• A Hawaiʻi resident (kamaʻāina). You may be able to join the free Kamaʻāina Observatory Experience, which takes residents inside a working summit observatory on the first Saturday of most months, now with 28 places split between two facilities. It is the closest anyone gets to the real telescopes, and it is for residents only.

Our Recommendations

1. To look through a telescope: book a Big Island summit-and-stars tour (about $255 to $330 on GetYourGuide, usually with an 11-inch Celestron, and no under-13s) for eyepiece views of the planets and the Moon, or reserve the free VIS monthly telescope night well ahead. On Maui, go to one of Haleakalā’s free ranger programs.
2. To see a famous research telescope: visit the Keck Visitors’ Gallery (daily, 10:00 a.m. to 2:30 p.m.) and view Keck I through the gallery window. Do not expect to look through it.
3. With children under 13: skip the summit and choose a resort or beach stargazing program, the VIS event or ʻImiloa.
4. Before you travel: take the Keck 360° and Subaru 3D virtual tours, and try a free MicroObservatory image request, so you arrive knowing how these machines really work.
5. If the trip inspires a purchase: start with 10×50 binoculars, then move up to an 8-inch Dobsonian for visual deep-sky observing, or a ZWO Seestar S50 (about $499) for easy deep-sky imaging. If the planets are your priority, buy aperture and good optics, not a smart telescope.

What would change this advice. More decommissioning or new access policies could change what is open, so re-check the gallery hours and the KOE and VIS reservation systems before you book. A new smart telescope, such as a Seestar S50 Pro, would change the prices above. And if a tour operator switches instruments, confirm the telescope before you pay. If you want to photograph the sky yourself rather than look through glass, our Mauna Kea astrophotography field guide covers where you can legally set up after dark and what to pack.

Notes on Sources and What Is Changing

• Prices and models change quickly. Smart-telescope prices and lineups change often; the figures here come from retailer and reviewer reporting in late 2025 and 2026 (Skies & Scopes, AstroForum, Cloudy Nights) and should be checked again when you buy. Where sources quoted different prices, we have given a range. Tour prices and age limits vary by operator and season; the GetYourGuide prices and ratings above were checked in October 2026.
• Program schedules shift. The VIS telescope event is monthly, depends on weather and staffing, and is by reservation only. The Kamaʻāina Observatory Experience runs most months (not December or January) and is for residents only. Gallery hours and tour availability can change with the weather and mountain access.
• UKIRT is being removed. Its science operations ended on September 15, 2026, and removal is due to be finished by around 2030, so the number of telescopes and instruments on the mountain is changing.
• Access to Faulkes Telescope North is uncertain. The 2-meter telescope remains in the LCO network, but the original Faulkes Telescope Project education program appears to have wound down.
• Queue and classical shares differ by observatory and are not published as a single figure; the general picture (Gemini heavily queue-scheduled, Keck more classical) is reliable, but the exact percentages vary by semester.
• IRTF’s size is quoted two ways. NASA and the Institute for Astronomy describe a 3.0-meter telescope; its primary mirror measures 3.2 m. Both figures appear in good sources.

For what you can see and visit at the summit itself, the observatories guide has the details, and the complete guide to Mauna Kea stargazing tours compares every operator and price.