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Haleakalā Observatory
Pan-STARRS surveys for moving objects from this summit — it found ‘Oumuamua — alongside the 4 m Inouye Solar Telescope, the highest-resolution view of the Sun there is.
- Where
- Maui, Hawai‘i
- Coordinates
- 20.71°N 156.26°W
- Since
- 1961
- On the map
- Show me
- More
- ifa.hawaii.edu
The sky from here
This is a zone 2 sky — rural on the nine-grade scale, Bortle 2–3, reaching roughly magnitude 6.7–7.5 unaided. 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.
That grade puts 107 of the catalogue within easy reach of 10×50 binoculars and 107 within a 130mm — 44 of them need no instrument at all. There is nowhere darker worth driving to; this is already among the better skies on the planet.
There is no season here in which the sky fails to get properly dark — the Sun clears eighteen degrees below the horizon on all 365 nights.
The centre of the galaxy climbs to 40° 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, 1 never set from here and every one of them rises at some point in the year.
Of everything in the catalogue, Beehive Cluster, Black Eye Galaxy and Crab Nebula are the best served here, climbing to within a few degrees of straight up — 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.
Cigar Galaxy never set from this latitude, so they are available on any clear night of the year rather than for one season of it.
Read at 20.71°N 156.26°W. Darkness is estimated rather than measured; everything else follows from the latitude and holds along the whole parallel. How accurate this is.
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Questions
What part of the sky never rises at Haleakalā Observatory?
Everything south of declination −69°. From 20.7°N that is a cap 21° in radius centred on the south celestial pole, which is 3.2% of the whole celestial sphere. It is out of reach permanently rather than seasonally: no time of year and no instrument brings it above the horizon. The matching 3.2% around the north celestial pole is the same geometry inverted, and never sets.
How many hours of true darkness does Haleakalā Observatory get?
Between 7 hours 47 minutes on the shortest night of the year, around 21 June, and 10 hours 29 minutes on the longest, around 21 December. Astronomical darkness is the Sun more than eighteen degrees below the horizon, which is a stricter thing than the Sun being down. The sky here reaches it on every night of the year, which is not true much further from the equator.
When is the Milky Way best from Haleakalā Observatory?
Around 17 June, when the galactic centre transits at local midnight, and usefully from about May to September — earlier each evening as the season goes on. 20.7°N is close enough to the equator that the sky reaches full astronomical darkness on every night of the year, so unlike sites further north there is no part of the season where the core is high and the sky refuses to cooperate.
How far is Haleakalā Observatory from the other sites on this map?
Its closest neighbour on this map is Mauna Kea Observatories, 128 km away to the south-east. That is also the nearest other observatory, with the next one 4,030 km beyond it. Measured as the great circle between coordinates, which is the shortest path across the surface and rarely the one you could travel.