Universe Today
Places · Observatory
Mauna Kea Observatories
Thirteen instruments at 4,200 m, including Keck I and II, Subaru and the JCMT. The summit is sacred ground to Native Hawaiians, and the question of what may be built there is unresolved.
- Where
- Hawai‘i, United States
- Coordinates
- 19.82°N 155.47°W
- On the map
- Show me
- More
- ifa.hawaii.edu
The sky from here
The sky over this spot is zone 2 — rural, Bortle 2–3, with a naked-eye limit around magnitude 6.7–7.5. The Milky Way is structured and obvious. Light domes sit low on the horizon over distant towns, and the rest of the sky is genuinely dark.
Against that sky 107 of the 110 Messier objects are straightforward in 10×50 binoculars and 107 in a 130mm, with 44 reachable by eye alone. There is nowhere darker worth driving to; this is already among the better skies on the planet.
The Sun drops far enough below the horizon here for full astronomical darkness on every night of the year — which is not true of anywhere much further from the equator.
The centre of the galaxy climbs to 41° at its best — high enough that the summer Milky Way is genuinely three-dimensional rather than a band low in the south. Of the 110 Messier objects, none are circumpolar and every one of them rises at some point in the year.
The sky here is kindest to Beehive Cluster, Black Eye Galaxy and Crab Nebula, each of which passes within a few degrees of overhead — an object at the zenith is being seen through the least air it will ever be seen through, and the difference against the same object low in the south is not subtle.
Read at 19.82°N 155.47°W. Darkness is estimated rather than measured; everything else follows from the latitude and holds along the whole parallel. How accurate this is.
In the news
Phys.org
European Spaceflight
AAS Nova
Nearby
Questions
What part of the sky never rises at Mauna Kea Observatories?
Everything south of declination −70°. From 19.8°N that is a cap 20° in radius centred on the south celestial pole, which is 3.0% of the whole celestial sphere. Nothing about the calendar or the aperture changes that — the cap is below the horizon at every hour of every night. Its mirror image, the same 3.0% around the north celestial pole, is circumpolar here and never goes down.
How many hours of true darkness does Mauna Kea Observatories get?
From about 7 hours 52 minutes at the thin end of the year, near 21 June, up to 10 hours 27 minutes around 21 December. The measure is astronomical darkness — the Sun a full eighteen degrees under — not simply the hours between sunset and sunrise. Unlike sites further from the equator, no part of the year here is written off entirely.
When is the Milky Way best from Mauna Kea Observatories?
From roughly May to September, peaking around 17 June when the core is on the meridian at midnight and drifting into the evening sky thereafter. The useful thing about 19.8°N is that every one of those nights actually gets dark — at higher latitudes the best weeks of the core season are also the weeks with no astronomical night at all.
How far is Mauna Kea Observatories from the other sites on this map?
Haleakalā Observatory is the nearest thing to it here — 128 km to the north-west. That is also the nearest other observatory, with the next one 4,010 km beyond it. These are straight-line distances over the surface, not driving distances, and in this part of the world the two can differ considerably.