by Josh Walawender


Visiting Hawaii:  A Guide for the Astronomy Enthusiast

If you want to use the sites above the VIS, you’ll need a four wheel drive vehicle to get up there.  Also, check in at the VIS to let them know.  The rangers generally try to shoo people of the summit area after sunset, so you’ll want to make sure it is okay for you to stay and that they know what you are doing.

The third high altitude site is on Mauna Loa.  Just below the Mauna Loa Atmospheric Observatory around 11,000 feet is a small parking lot for the hiking trail to the summit.  This site allows you to get to a higher elevation than the VIS without needing four wheel drive.  The road is one lane and rough, but is quite passable by a passenger car.  Like the other high altitude sites discussed here it has no amenities.

If you’re on Maui, Haleakala is another excellent observing site.  I’m not as familiar with it, but the Haleakala Amateur Astronomers club (HAA) is quite friendly and they have a small observing site there.  As with all high altitude sites, wind will likely be the biggest problem while observing.

Commercial Tours

There is one other way to do observing on Mauna Kea and that is to take a commercial tour.  These start around $200 per person and they drive you up to the summit for a tour and to watch sunset (no observatory access).  Warm jackets and a meal are provided, and you get a short observing session lower down on the slopes after dark.  These usually use 8-11 inch SCTs and last about an hour.  The quality and accuracy of the stargazing session can vary significantly depending on the individual tour guide. If you’re coming with family who wouldn’t be interested in staying for a full multi-hour observing session and don’t want to bother bringing heavy jackets or renting a four wheel drive vehicle, this is a good option.

Local Resources

There are two astronomy clubs on the Big Island.  The larger and more active club is the West Hawaii Astronomy Club (WHAC).  They meet monthly in Waimea at either the Keck or CFHT headquarters.  They have an online discussion group on Yahoo! Groups (search for WHAC) which can be quite helpful.  In addition to WHAC, there is a smaller club based in Hilo.  The Hilo Astronomy Club (HAC) is currently less active in that they have no regular meetings, but has an on line discussion group on Yahoo! Groups (search for HiloAstro) and regularly goes observing at the VIS.  Both clubs welcome queries from visitors so don’t hesitate to log on and post a question.

Final Thoughts

I hope this encourages some of you to visit the islands.  This is a remarkable place astronomically, geologically, ecologically, and culturally.  There’s no where else on the planet as isolated as Hawaii is in the middle of the Pacific Ocean.  Despite, or perhaps because of that, it has a unique culture and environment and different visitors all with diverse interests will find something remarkable here to enjoy.

Part I:  Introduction to Hawaii and Mauna Kea

To most people’s minds, Hawaii conjures up images of luxurious tropical sun, beautiful beaches, mai tais, and flowered shirts.  To astronomers, on the other hand, it represents dark nights, clear skies, and access to southerly constellations (and maybe some mai tais and beach time on the side).  I’ve lived here in Hawaii (on the Big Island) for a few years and have met visitors from all over through volunteering at the Mauna Kea Visitor Information Station and by giving a few tours through my work with the University of Hawaii.  I’m occasionally contacted by amateur astronomers who are planning on visiting Hawaii and are interested in seeing the observatories or in doing some observing here.  As a result I’ve compiled advice for visitors interested in astronomy and Mauna Kea in particular. 

I’ll start this article with an introduction to Hawaii in general and the observatories on Mauna Kea in particular.  Later on I’ll summarize my advice about visiting the island for astronomy.

Sunset at Hapuna Beach State Park on the Big Island of Hawaii

The Hawaiian Island Chain and Hawaiian Volcanos

As some visitors know, Hawaii can refer both to the entire state, or to the island of Hawaii.  Some will make the distinction between being ‘in Hawaii’ (the state) or ‘on Hawaii’ (meaning the island), but I’ll refer to the Island of Hawaii as ‘The Big Island’ to avoid confusion.  There are eight main islands in the Hawaiian chain, four of which are major tourist destinations (Kauai, Oahu, Maui, and The Big Island).  The majority of this article is about The Big Island, but I’ll mention other islands briefly near the end.  What makes The Big Island such a destination for astronomy is its mountains.

The Hawaiian island chain is made up of volcanos which form above a ‘hot spot’ in the Earth’s crust where magma billows up, and emerges on the sea floor.  These volcanos  build up until they breach the surface and become a volcanic island.  As the Pacific plate moves across the hot spot, the volcanic activity moves south and east along the island chain.  Therefore the oldest islands are to the northwest (i.e. Kauai) and the youngest are to the southeast (The Big Island). 

The Big Island truly deserves its nickname.  Its land area is larger than all the other Hawaiian Islands combined.  It is made up of five volcanos (Kohala, Hualalai, Mauna Kea, Mauna Loa, and Kilauea).  Another volcano, Lo’ihi, is currently building a new island a few thousand feet below the waves, just off the south coast of the Big Island.  The oldest volcano, Kohala, forms the north part of the island.  It is extinct and heavily eroded, appearing more as a ridge line than a mountain.  Hualalai is an 8,271 foot peak which overlooks the resort areas on the Kona Coast.  Odds are, if you’re staying on the Big Island, you’re on the Kona Coast in view of Hualalai.  Hualalai is considered dormant (not extinct), so don’t get too comfortable.  It last erupted around 1801.

Mauna Loa dominates the island.  It is the largest active volcano on Earth and last erupted in 1984.  Like Olympus Mons on Mars and most other Hawaiian volcanos, it is a ‘shield’ volcano,  meaning that the lava which erupts from it is fairly liquid and flows out and down the slopes forming the smooth gradual slope of the volcano.  Because the slope is so gradual, Mauna Loa can sometimes appear deceptively small and nearby.  From certain vantage points on the island Mauna Loa can seem to be a nearby hill only a few hundred or few thousand feet high (see photo).  In fact, the summit is 13,679 feet (4,169 meters) above sea level, high enough that it can be snow capped in winter, even here in the tropics.  Because its slopes are so gradual, Mauna Loa contains an enormous volume of rock.  The mountain is so massive that the crust of the Earth is depressed underneath it by its bulk.

Mauna Loa as seen from Hawaii Volcanos National Park.  Though it looks like a low hill, Mauna Loa’s summit is 13,679 feet above sea level.  Mauna Loa’s summit is technically within the boundaries of the National Park.  The park is unique in that it encompasses climate zones ranging from from sea level coastline, to the summit of Mauna Loa.

Kilauea is the most active volcano on the planet.  Erupting almost continuously since January 1983, it is forming new land on the southern edge of the island.  Kilauea sits on the slopes of Mauna Loa. Despite how it might appear, it is a distinct volcano.  It has it’s own magma chamber and its lava is chemically distinct from Mauna Loa’s lava.  Kilauea is the main attraction of Hawaii Volcanos National Park which is definitely worth the trip if you’re on the island.

Lava flows in to the sea in Hawaii Volcanos National Park.

The most visually striking of the five volcanos is Mauna Kea.  Dormant like Hualalai, it last erupted about 4,500 years ago.  In the latter stages of its active life, it evolved past the shield stage and erupted with more cinematic explosions, hurling lava in to the air.  This built up steeper slopes and numerous cinder cones (or pu’us).  This gives Mauna Kea a sharper profile than Mauna Loa.  It is also slightly higher with its summit at 13,802 feet (4,207 meters) above sea level.  Measured from its base on the ocean floor to its summit, Mauna Kea is the tallest mountain on Earth. It is taller than Mount Everest, though Everest’s summit is farther above sea level because Everest sits on the continental shelf rather than the ocean floor.

Mauna Kea’s snow capped peak as seen from Hilo Bay on the east side of the Big Island.

Mauna Kea Observatories

Interestingly it is Mauna Kea’s sharp profile which is one of the features that makes it particularly suitable for astronomy.  When searching for an observatory site, astronomers look for three features above all others:  dark skies, minimal cloud cover, and good seeing.  Mauna Kea excels in all three categories.  Its location in the middle of the Pacific Ocean means there is little in the way of light pollution.  Only around 150,000 people (as of the 2000 census) live on the Big Island.  The largest city is Hilo with about 40,000 people.  The city of Honolulu is 180 miles away on Oahu.  Local light pollution from Hilo and Kona is often eliminated by the presence of clouds associated with the tropical inversion layer.  The inversion layer is a boundary between warm moist air below and very dry, cooler air above.  The interface generates clouds.  When conditions are stable (as they usually are here), the inversion layer sits between five and eight thousand feet.  The summit of Mauna Kea projects up in to the clear, dry air above the inversion layer.

Because of its unique location, Mauna Kea also boasts some of the best seeing on the planet.  Turbulent air flow, which would normally blur starlight, is minimized because air flow is uninterrupted by land forms here in the middle of the Pacific Ocean.  Mauna Kea’s steeper slopes thrust the observatories at the summit up into the smooth flow of air above the islands.  Seeing on the summit is often around 0.5 arcseconds and on exceptional nights, it can be even less.

The air at the summit is also dry.  Relative humidity can be less than 10%.  When combined with its altitude, which places it above 40% of the Earth’s atmosphere, this means that astronomy can be done on Mauna Kea at longer wavelengths in the infrared and submillimeter.  Light at these wavelengths is usually blocked by water vapor in the Earth’s atmosphere, but here on Mauna Kea the infrared and submillimeter sky is literally transformed from opaque to transparent.

The Mauna Kea Summit telescopes.  The Kohala mountains are behind the telescopes and Haleakala on Maui can be seen in the distance.  Image copyright Richard Wainscoat, all rights reserved.  Used with permission.

As a result of these factors, Mauna Kea is now one of, if not the, finest observatory sites on the planet.  It has the largest collection of research telescopes anywhere in the world.  Eleven major research telescopes grace its summit area.  This includes four optical telescopes 8 meters or larger, two of which (the twin Keck telescopes) currently share the title of worlds largest optical telescope.  Two other telescopes, one for education and one well below the summit, round out the thirteen total telescopes on Mauna Kea.

The telescopes on Mauna Kea (from smallest to largest) are:

The UHH 24/36 inch:  This is the smallest dome on the mountain.  Up until fall of 2008, it contained a 24 inch telescope which was one of the oldest on the mountain.  Owned and run by the local University of Hawaii at Hilo, it is used a teaching tool for students.  It is currently being removed and the telescope is currently being replaced by a 36 inch telescope which will be remotely operated.

The UH 2.2 meter:  Also known as the UH 88 inch telescope, this is the oldest “large” telescope on the mountain.  Built in 1970, it proved that Mauna Kea was one of the finest observatory sites on the planet.  Its success paved the way for future telescopes.

The 3 meter NASA IRTF:  One of three observatories finished in 1979, the NASA Infrared Telescope Facility (IRTF) was built primarily for planetary science.  It takes advantage of the extreme clarity (at infrared wavelengths) of Mauna Kea’s dry atmosphere.  This telescope has supported many of NASA’s great interplanetary space missions such as Voyager.

The 3.6 meter CFHT:  The Canada France Hawaii Telescope (CFHT) was also built in the late 70s and, when completed, was one of the finest research telescopes anywhere in the world.  The conditions on Mauna Kea made this 3.6 meter telescope’s performance competitive with larger 4 and 5 meter telescopes located elsewhere.  CFHT continues to be well instrumented with large, prime focus cameras for optical and infrared imaging.

The 3.6 meter Canada France Hawaii Telescope (CFHT).

The 3.8 meter UKIRT:  Also finished in the late 70s, the United Kingdom Infrared Telescope was designed solely for infrared astronomy.  It is optimized to work at wavelengths from 1 to 20 microns (visible light is 0.4-0.7 microns wavelength).  It remains the largest infrared-only telescope in the world.

The 3.8 meter United Kingdom Infrared Telescope.

The 8.1 meter Gemini North Telescope:  Gemini North is one of a pair of identical telescopes (the other is on Cerro Pachon in Chile) designed to provide access to both hemispheres of the sky.  Gemini is an infrared optimized telescope, though it also does significant work in visible light.  Finished in 1999, it is the crown jewel of the United States’ National Optical Astronomy Observatory, but is also an international collaboration.  The US owns 50% of both telescopes, the remainder is shared by the United Kingdom, Canada, Australia, Brazil, Argentina, and Chile. 

Unlike the older telescopes described, Gemini is a modern telescope design which utilizes an alt-az mounting making it much more compact than previous generations of telescopes which were built with massive, steel Palomar-style equatorial mountings.  To an amateur astronomer, these large telescopes are the high tech equivalent of a dobsonian.  Gemini’s primary mirror is a single piece of glass only 20 cm (less than 8 inches) thick.  It is shaped like a meniscus (similar to a contact lens) and is supported by a complex system of actuators which ensure that the surface does not warp under its own weight.  Gemini has five instruments installed at cassegrain focus behind the primary.  The instruments behind the mirror are so heavy and the primary mirror so light, that the balance point of the telescope is actually slightly behind the surface of the primary mirror.

The  8.1 meter Gemini North Telescope with CFHT in the background.

The 8.2 meter Subaru Telescope:  Built by the National Astronomical Observatory of Japan in 1999, Subaru is a masterpiece of engineering.  The most expensive individual telescope on Mauna Kea, it is unique in that it is the only 8 meter class telescope in the world to have a  prime focus camera.  This camera (SuPrimeCam) is placed at the f/1.83 focus above the primary mirror as opposed to the cassegrain or naysmith foci as on other large telescopes (which tend to operate at much slower f-ratios around f/10).  Successfully operating a prime focus camera means suspending a massive structure 15 meters above the primary mirror and holding it in place with a tolerance of a few microns.  The camera, filter exchange system, and field derotator must all be positioned precisely as the telescope moves.  This means Subaru has an expensive and massive truss structure.  Gemini (and other 8 meter class telescopes) appear thin and lightweight by comparison.

The 8.2 meter Subaru Telescope.

The 10 meter Keck Twins:  Currently the largest optical telescopes in the world, the Keck telescopes use unique segmented primary mirrors made up of 36 hexagonal segments.  Finished in 1992 and 1996 the light from the two telescopes can also be combined interferometrically to give the resolution (not light gathering) of a telescope 85 meters across.

The 10 meter Keck Telescopes.

Keck, Gemini, and Subaru are all equipped with Adaptive Optics (AO) systems to compensate for the blurring effect of the atmosphere (seeing).  This technology, used primarily at wavelengths in the near infrared (just beyond visual light), can produce very sharp images over a very small area of sky.  All three telescopes use laser guide stars for their AO systems in which a powerful (usually 8-30 watt) laser is propagated upward.  It excites a layer of sodium atoms high in the atmosphere, generating an artificial star which can then be used as a reference for the AO system.

The Keck laser guide star in action.

The Caltech Submillimeter Observatory (CSO):  Below the summit ridge line where the optical and infrared telescopes are located is “Submillimeter Valley” where three submillimeter telescopes take advantage of the clarity of Mauna Kea’s dry atmosphere.  These telescopes have more in common with radio dishes than optical telescopes.  CSO is in fact an enhanced 10 meter radio dish modified to work at the shorter submillimeter wavelengths.

The James Clerk Maxwell Telescope (JCMT):  Built by the United Kingdom and operated in concert with UKIRT, the JCMT is a 15 meter submillimeter telescope.  JCMT is unique in that it can observe during the daytime using a gore-tex shield which is stretched over the dome slit.  Gore-tex is mostly transparent to submillimeter light and keeps the sun off of the dish.  If the sun shines on the dish, it would warm  and distort the optical surface.

Submillimeter Valley with CSO (left), JCMT (center), and SMA (right).

The Submillimeter Array (SMA):  Run by the Smithsonain, the SMA is an array of eight 6 meter dishes which are used in concert as an interferometer.  The dishes can be moved around to simulate the resolution of telescopes of varying diameters.  Smaller, compact arrays have greater sensitivity, but the larger, more spread out arrays provide the best resolutions.  A single science observation may utilize the telescope in several different configurations over time to build up a complete picture.

The VLBI Station:  The thirteenth telescope on Mauna Kea is actually well below the summit at about 12,200 feet elevation.  This 25 meter radio dish is part of the Very Long Baseline Interferometer (VLBI) which combines the signals from radio dishes spread across an entire hemisphere.  Central to this system is the Very Large Array (VLA) in New Mexico, but other stations stretch out all the way to the Caribbean.

Development on Mauna Kea

The development of Mauna Kea’s summit area has been a matter of some debate.  Several groups, including native Hawaiian groups in particular, oppose further development.  To the native Hawaiians Mauna Kea is a sacred place where Poli’ahu (goddess of snow) battled and defeated Pele, the goddess of fire.  Pele now lives in Kilauea, leaving Mauna Kea under the influence of Poli’ahu and her sisters Lilinoe (goddess of mists) and Waiau (goddess of the lake).

Controversies over development came to a head in the 1990s and early 2000s regarding the Keck Outrigger project, which would have put several small 1.8 meter telescopes around the Keck twins in order to enhance their interferometric capabilities.  This project is similar to one which the European Southern Observatory put in place around its 8 meter VLT telescopes.  The environmental impact study for the project was challenged in court.  Appeals and proceedings dragged on until NASA cancelled the project.  A result of this was that a new “Comprehensive Management Plan” has been formed to govern the operation and further development of Mauna Kea’s summit area.

Mauna Kea’s summit is the “preferred site” for the proposed Thirty Meter Telescope (TMT) which is primarily a collaboration between The University of California and CalTech, the same collaboration who built the Keck telescopes.  When built, it would be the largest optical telescope in the world.  In addition to TMT, the Pan-STARRS project wants to replace the current UH88 telescope with a new dome containing four co-mounted 1.8 meter, wide field survey telescopes.  Pan-STARRS, which is operating a single testbed telescope on the summit of Haleakala on the island of Maui, will make a weekly survey the sky to search for all Earth crossing asteroids larger than 300 meters across.  These are the potentially dangerous asteroids which could cause local or planetary devastation if one were to collide with Earth.

With the new management plan, the planned construction of TMT, and the potential replacement of the UH88 with  Pan-STARRS on the horizon, the future of Mauna Kea as a world class astronomical observatory appears to be secure.  However, two telescopes on the mountain face uncertain futures due to funding.  Cal Tech expects to decommission the CSO before the end of the decade and UKIRT operations are being downsized to a low cost, minimalist mode and its long term future is uncertain.  In the end, I expect there to be fewer telescopes on Mauna Kea in the decades ahead, but those that remain will be some of the finest facilities on the planet.

Other Astronomical Sites

Also on the Big Island is the summit of Mauna Loa.  Though its status as an active volcano certainly discourages development, it does have a small atmospheric observatory run by the National Oceanic and Atmospheric Administration (NOAA) on its slopes at 11,135 feet above sea level.  Mauna Loa’s location in the middle of the Pacific isolates it from the influence (i.e. pollution) of large urban areas.  Effects from nearby cities are usually trapped by the inversion layer which allow its instruments to sample undisturbed atmosphere.  The most famous experiment at Mauna Loa Observatory (and one of the reasons for its founding) is an experiment begun in 1958 by Dr. Charles David Keeling to measure the carbon dioxide content of the atmosphere.  Data from this experiment shows the carbon dioxide content of the atmosphere rising steadily over the last 50 years, likely a result of the burning of carbon based fuels.  The ‘Keeling Curve’ was made famous when it was used in congressional hearings about global warming and was featured in the documentary An Inconvenient Truth.

Mauna Loa Observatory also hosts a few astronomy related experiments.  A solar observatory has been operating there to monitor the sun and a new submillimeter telescope to examine the cosmic microwave background radiation has just begun operating.

The island of Maui also has a tall mountain which is suitable for astronomy.  Haleakala, whose summit reaches 10,023 feet above sea level, hosts an observatory.  At this elevation, the inversion layer clouds the summit more often than on Mauna Kea, but several telescopes reside here.  Initially built as a solar observatory, Haleakala still hosts several solar telescopes and will soon have the latest generation of solar telescope.  The Advanced Technology Solar Telescope (ATST) will be a four meter unobstructed off axis reflector which will study the Sun with unprecedented detail.  Also on Haleakala is PS1 (the Pan-STARRS testbed telescope) and the Faulkes Telescope North.  Faulkes is a 2 meter telescope built solely for educational use.  The Maui based Haleakala Amateur Astronomers also have a small site on the summit where they observe.

None of the other islands in the Hawaiian chain have high mountains which routinely emerge from the inversion layer, so Haleakala, Mauna Loa, and Mauna Kea remain the only major research observatories in the state.

Part II:  Visiting Mauna Kea

If you’re coming to the Big Island, you’ll fly in to either Hilo airport (on the east side of the island) or Kona airport (on the west).  Kona is the more glamourous and touristy destination with large resort hotels and golf courses along the coastline.  The majority of island visitors come here to enjoy the frequent sunshine and incredible beaches.

Mauna Kea as seen from the Waikoloa Beach area on the Kona side of the Big Island.

From Kona Airport, the Visitor Information Station (VIS) on Mauna Kea (at 9200 feet) is about a 65 mile drive which takes around two hours.  The saddle road, which crosses the island between Mauna Kea and Mauna Loa is a rough, windy road on the Kona side.  The pavement is a rough patchwork for the lower few miles and the road is narrow, with several small one lane bridges.  The road is paved and so is passable by passenger car, but some rental companies forbid you from driving it, so check your rental agreement.  As I’m writing this there is a major improvement project ongoing on Saddle Road.  Most of the old bad road has been resurfaced and in parts, a new, straightened road is being built which will eventually meet the upper road in Kona at a different location than the current saddle road.  Note that there is no gas available anywhere along the road and you’ll be gaining significant elevation, so be sure you start the drive with a full tank.

The Hilo side is much less glamourous than Kona.  You won’t find any mega-resorts here.  The Hilo side faces the trade winds, resulting in moisture being pushed up against the mountains and squeezed out of the clouds as rain.  Hilo airport officially gets about 130 inches of rain per year, but other locations in town get nearly double that.  Also, the beaches on the Hilo side weather differently and are more rocky, without the classic arc of white sand that people expect from Hawaii.  As a result, Hilo gets minimal (by Hawaii standards) tourist activity.  Hilo does have some attractions for those willing to brave the rain (which mostly falls at night anyway).  Because of the rain, Hilo is a lush tropical forest.  Several botanical gardens are in the area and the drive north along the Hamakua coast is spectacular.  Hilo is also the obvious jumping off point for a visit to Hawaii Volcanos National Park to see Kilauea Volcano (which should be part of any Big Island visit).  For the astronomy enthusiast, Hilo also has the Imiloa Astronomy Center, a planetarium and science museum.  The planetarium is currently the only one in the world equipped with full dome 3D projectors.

From Hilo, the drive up to Mauna Kea is much easier.  It consists of a 37 mile (roughly 1 hour) drive from Hilo Airport over the new and improved saddle road.  Though it is winding in the bottom half, it is fully two lanes and smooth (unlike the Kona side).  Above the 19 mile marker, the road is brand new.

Whichever side you approach from, the saddle area (at around 6,000-6,500 feet above sea level) is incredibly scenic.  Approaching the Mauna Kea access road from the Hilo side (the access road is just before the 28 mile marker) you drive through a barren lava flow from a 1935 eruption of Mauna Loa.  Just opposite the turn to Mauna Kea, is Pu’u Huluhulu (furry hill), a ‘kipuka’, an island of old vegetation which sits in the middle of a more recent lava flow which destroyed the forest around it.  Just a few miles past the access road toward Kona is Mauna Kea State Park, which has some cabins available for camping.  If you intend to spend a few days (or nights) enjoying the mountain, this may be a good option in that it saves you several hours of driving, though it is much rougher living than a Kona resort.

Pu’us in the saddle between Mauna Kea and Mauna Loa.

After you make the turn up Mauna Kea, you’ll wind upwards through the ranch lands, climbing in to the Mauna Kea Forest Reserve.  After 6 miles you’ll come to the Visitor Information Station (VIS) on your right.  This is the end of the paved road.

The Mauna Kea Visitor Information Station

The VIS is your final destination if you’ve come in a two wheel drive passenger car.  It has a small gift shop, some displays, and informational movies are played through the day on astronomy, geology, and Hawaiian culture (or anything else you can convince the staff to play, they’d probably welcome the change).  There is a very short hike behind the VIS which takes you in to a Silversword preservation area.  Mauna Kea Silversword is a unique endangered plant that blooms only once in its 50 year lifespan.

Mauna Kea Silversword in Bloom.

There is also a nice hike across the road from the VIS which takes you up to the top of a nearby pu’u (see photo).  This provides the best view of sunset that you’ll get short of making the trip to the summit.  Just above the VIS is Hale Pohaku (HP).  These buildings are the cafeteria and dorms for the observatories.  Staff and visiting astronomers sleep here at the much more hospitable elevation of 9,200 feet rather than on the summit.

The shadow of a pu’u crosses the VIS (building near center) and Hale Pohaku (complex of buildings toward the upper left).

Climbing Higher

Above HP, the road becomes gravel.  It is steep with several sharp switchbacks.  The road conditions change constantly with weather and traffic.  Washboard can be truly dreadful here even though the road is graded twice a week, so how you find it will depend a lot on when you happen to see it relative to the grading schedule and how much recent traffic there has been.  This is where a four wheel drive vehicle becomes important, not because you need to climb over obstacles, but because you need the traction.  You’ll see two wheel drive passenger cars making this trek and you may be tempted to try it if you don’t have a four wheel drive vehicle, but please don’t.  Four wheel drive is less important for the way up than it is for the way down where you’ll want the lower gear ratios and extra traction.  The Mauna Kea Rangers have to assist a good fraction of those who venture up in a two wheel drive vehicle.  If you’re still tempted to try it in a two wheel drive vehicle, keep in mind that a tow from this remote location will run you nearly $1,000 and that’s before they do any work on the car.

In addition to the road, you also have to watch out for altitude sickness.  Regardless of where you’re from or what elevation you’re used to, you’ve probably been sleeping and living very near sea level on this trip.  A climb to almost 14,000 feet is a shock to the system and potentially dangerous.  Stay hydrated (it helps to drink plenty of water before going up), don’t ignore warning signs (headache, dizziness, fainting, etc.), and get help if you need it.  The Rangers carry oxygen for emergencies, but the only cure is to go down to a lower elevation.  This will immediately help if you’re feeling ill.  If you’re headed up the mountain, spend at least half an hour (an hour is better) at the VIS to acclimatize before continuing on to the summit.

Lastly, be sure to dress warmly.  Even in summer, the summit highs will only be in the 50s, and with wind and the thin air it will feel a lot colder.  If you’re on the summit near sunset, prepare for near freezing temperatures (and remember, stiff winds are the norm, so windchill makes it feel worse).

That said, the road higher up is spectacular.  You get great views of the saddle, Mauna Loa, and some of Mauna Kea’s pu’us (cinder cones).  The road becomes paved again as you near the top (to keep dust down around the observatories).  You’ve now entered the Mauna Kea Ice Age Natural Preserve.  Mauna Kea had permanent ice cap during the last ice age (around 10 to 20 thousand years ago).  Those of you with an eye for geology will see evidence of this including moraines (rock piles deposited by receding glaciers).  Look for just such a moraine out the right side of your car as you get back onto pavement after the dirt road ends.

The glaciers existed while Mauna Kea was still active.  As a result, lava sometimes erupted underneath a sheet of ice.  This cooled the lava more rapidly forming a harder rock which the native Hawaiians quarried and used to make adzes.  These stone tools were prized trading goods and examples of Hawaiian stone tools quarried at this site have been found on remote islands across the Pacific.  They were apparently valued trading goods across thousands of miles of ocean.

The Summit

The first (close up) view you’ll get of telescopes on the summit will be as you come around one of the final curves on the climb.  The telescopes of Submillimeter Valley (CSO and JCMT) will emerge in the foreground and Subaru and Keck will come in to view on the ridge behind them.  Coming around a hairpin turn, you’ll have the choice of either going left into submillimeter valley or heading uphill toward the ridge line.  I recommend the ridge line. 

The Subaru and Keck Telescopes with the Sun setting behind them.

The first telescope along the ridge is the UHH 24 inch (soon to be 36 inch).  Behind it, you’ll see UKIRT, the UH88, Gemini, and CFHT.  The road forks, continue straight and park in the open area near the UH88.  This is a great area to watch sunset, which can be truly spectacular from here.  The best sunsets often come when there is some thin cirrus to reflect the sunset colors (see photo).  To drive out to the IRTF, Keck, and Subaru, take a left back at the fork in front of UKIRT.

The actual summit of Mauna Kea (Pu’u Weiku) is undeveloped.  You’ll see the summit and the trail leading there across the road from the UH88 and UKIRT telescopes.  The structure on it is a small native Hawaiian altar.

Access inside the telescopes is limited.  These telescopes are essentially industrial work areas (i.e. hard hat zones), so conducting tours is not something most telescopes do.  There are a few options though:  Keck has a viewing gallery which is open 10AM to 4PM Monday through Friday.  The gallery has a few posters and a viewing room where one can walk out in to an enclosed area of the telescope floor to get a look at the giant telescope.  Subaru and Gemini offer tours of their telescopes (usually for groups), but arrangements need to be made beforehand.  Check their web sites or call them for current information on tours.

The VIS offers guided summit tours on Saturday and Sundays.  Meet at the VIS at 1PM for a video orientation (which is also an important acclimatization stop).  You’re required to have your own transportation (they require a four wheel drive vehicle), but you’ll get a guided tour of the summit and a visit to the Keck viewing gallery from a VIS staff member or volunteer.


Mauna Kea’s reputation as an observational astronomy mecca lures amateur astronomers from the world over.  Unfortunately, the difficulty of traveling with a telescope, mount, eyepieces, warm clothes, and other gear makes many rethink bringing a telescope.  Having your own scope to use as you please is rewarding, but if you don’t bring one, there are other options such as the VIS nightly stargazing program (see below).

Mauna Kea enjoys relatively cloud free skies.  The key for observing is to get above the inversion layer.  It usually hovers around 6,000-8,000 feet, so much of Mauna Kea is above its clouds.  When there is additional moisture in the area from a nearby weather system, the inversion layer can climb higher, even reaching the summit on some nights.  The Mauna Kea Weather Center provides astronomy specific forecasts for the summit which are updated twice a day during the week.  It is a great resource for choosing which nights during your visit would be good for observing.

We are more likely to be clouded out in winter than at other times of the year, but your odds are still excellent for getting at least a few clear nights during your stay.  In my experience, what ruins the most observing nights is wind, not clouds.  The mountain is very exposed and as winds wrap around it they can shake your scope and make the night feel much colder.  This can wreak havoc on large cross section dobs or under-mounted scopes.

Observing at a high altitude site (above the inversion layer) can be very rewarding.  We have exceptionally clear skies here and the seeing (though much better up at the summit) is often very good down on the slopes of the mountain.  If you plan to observe, remember that you are at altitude and that it gets cold (yes, even here in Hawaii).  The temperature at 9,000 feet is often 30-45 degrees Fahrenheit at night.  This may not sound cold to some, but if you only packed clothes for Hawaiian beaches, it can be painful.

For most visitors coming from mid northern latitudes one of the appealing features of Mauna Kea (at 19.75 degrees North latitude) is access to southern skies.  One of my favorite times to observe from here is late Spring and early Summer.  At this time of year, the progression of southern objects is quite spectacular.  Starting in early April at the end of astronomical twilight the false cross in Carina is transiting.  The Carina Nebula (containing the supermassive star eta Carina) transits about two hours later.  Two hours after that, Crux (the Southern Cross) crosses the meridian.  Although low in the sky due to its declination, the Jewel Box cluster in Crux is quite beautiful.  About an hour after Crux follows Omega Centauri.  It is far more beautiful here than from the southern portions of the continental United States where I’ve observed it before.  It rises much higher from this latitude and that clears up the view spectacularly.  Before dawn breaks in early April, the center of the Milky Way becomes dominant in the night sky.  The additional contrast in the center of the Milky Way provided by the additional southern latitude (over my experience in the southern US) is dramatic.  Familiar nebulae stand out more clearly and dark clouds become stunning when the contrast with the background Milky Way improves.  This is where having a small, high quality, wide field travel scope that you are free to use as you please really pays off.  Sweeping the Milky Way from here is a special experience.  The center of the Milky Way is prominent through August, after which it is already descending in the West when the sky becomes dark.

The VIS Nightly Stargazing Program

The VIS has a nightly stargazing program every night of the year from 6PM to 10PM.  They set up telescopes and the volunteers and staff show the public the sky.  They also have nightly constellation tours.  Currently the VIS has a 4 inch refractor, a 14 inch SCT, and a 16 inch SCT that are run by volunteers and staff.  They are often more than willing to go to any object you  request (assuming there isn’t a big line of people taking up their time).  In addition, the VIS also sets up two to four dobs in the parking lot (4-8 inch aperture) which all visitors are welcome to use.  They’re often in poor shape because they are out every night and are available to anyone and thus are often handled roughly.  Thirty seconds of collimation work, though, often pays off with a significant improvement in the view.  Bringing your own eyepieces might also help as the ones used in them are often dirty and/or damaged.

The VIS observing area on a relatively low traffic night.

The VIS program suffers from one big disadvantage:  lights.  While the VIS itself does a good job keeping building lights red, the stargazing program takes place on a patio on the edge of the parking lot and that means headlights.  Depending on the day of the week and the weather, cars may be coming through periodically with their headlights on and the stargazing patio gets hit full on by many of them.  If this will bother you, then the VIS is probably not a good place for you.  The headlights problem decreases as it gets later and if the temperature drops, but it’s not uncommon to get a car coming through occasionally, even well after the VIS closes at 10 PM.  After the VIS closes, you can still observe from their parking lot (if you’ve brought your own equipment).  The advantage is that you’ve got access to water, bathrooms, and power.  Several time lapse movies of evenings at the VIS are available on my web site.

Other Observing Sites

There are several other high altitude sites which can be used for observing on the island.  They are all primitive without amenities (no water, no bathrooms, no power).  First, is the “power station” across the road from the VIS.  A short walk or a very short drive on the opposite side of the road from this VIS is a small transformer station and there is a flat clearing right in front of it.  One advantage to this site is that it is a short walk to the VIS where water and bathrooms are available all night if you should need them.  The downside is that this site is more exposed to wind than the VIS.

Alternatively there is the option of any of several higher altitude sites along the road above the VIS.  These include pull outs on the dirt section of the road and small parking areas at 12 and 13 thousand feet on the upper paved section.  Many are used by the tour companies for their observing sessions, but they usually clear out by a couple hours after sunset.  One big advantage of these sites is the altitude.  On nights when the inversion layer is higher than normal, they may be above the clouds when the VIS and other sites are socked in.  Conversely there is less oxygen at the higher elevations which makes dark adaption much more difficult, so you may actually lose some sensitivity by going higher.

A star trail image taken from the “power station” site across the road from the VIS.  The yellow lights are the astronomers dorms at Hale Pohaku.  The snaking trail of light cars on the gravel road which leads to the summit.  The red line in the sky is one of the laser guide stars used by the telescopes on the summit (which was not visible to the eye at this distance).