Hawaii, USA · 19.82°N 155.47°W · 4207 m
Stargazing in Mauna Kea
The best professional observing site on the planet — and altitude you must respect.
- Sky quality
- Bortle 2 — excellent dark sky
- Clear nights a year
- —
- Best month overall
- January
- Milky Way core
- February–October
The Milky Way shows structure and casts a faint shadow; the zodiacal light and airglow are visible to the naked eye.
Key facts
- Sky quality
- Bortle 2 — excellent dark skyBortle class 2
- Best Milky Way season
- February–OctoberPeak month: April, core reaching 41°
- Darkness quality
- Good10.5 h of astronomical darkness at its darkest, in December
- Best month for astrophotography
- DecemberAbout 12.5 dark, moon-free, statistically clear nights
- Coordinates
- 19.8207, -155.46814207 m elevation · Pacific/Honolulu
Questions answered on this page
- Is tonight good for stargazing in Mauna Kea?
- Is the Milky Way visible from Mauna Kea?
- How many clear nights does Mauna Kea get each year?
- What is the best month for astrophotography in Mauna Kea?
- How many hours of true darkness does Mauna Kea get each month?
- How dark is the sky in Mauna Kea on the Bortle scale?
- When is the Milky Way core above the horizon from Mauna Kea?
- Should I drive somewhere darker than Mauna Kea?
Mauna Kea's summit sits above 40% of the atmosphere and above the trade-wind inversion layer, which is why a dozen major observatories are built there. Seeing is routinely sub-arcsecond, transparency is extraordinary, and at 20° north both hemispheres' skies are partly accessible.
Visitors should stop at the Visitor Information Station at 2,800 m rather than the summit: it is the practical, legal and medically sensible place to observe, and the sky there is still exceptional. Altitude sickness at the summit is a real risk, not a formality.
Evergreen intelligence
The four questions people ask about Mauna Kea
Computed from astronomy for these coordinates and a full year of Sun and Moon geometry — not copied from anywhere.
- How many clear nights does Mauna Kea have?
- The cloud archive did not load for this location, so the clear-night count is unavailable right now. The darkness and Moon figures below are computed locally and remain valid.
- What is the best month for the Milky Way in Mauna Kea?
- April. The galactic centre clears 10° from February to October, and in April it reaches 41° while the sky is astronomically dark, with about 4.5 hours of usable core time a night.
- When is it darkest in Mauna Kea?
- December gives the most true darkness — an average of 10.5 hours a night with the Sun more than 18° below the horizon.
- When should I plan an astrophotography trip to Mauna Kea?
- December offers the most nights that are simultaneously dark, moon-free and statistically clear — about 12.5 of them. Book around the new Moon in that month and keep two spare nights; a single fixed date at any location is a coin toss.
Darkness calendar
Mauna Kea month by month
Astronomical darkness and Moon geometry are computed for these coordinates. Cloud figures are ten-year ERA5 daily means. Rating combines darkness, moon-free nights and clear-sky odds.
| Month | Astro darkness | Moon-free dark nights | Avg cloud | Clear nights | Milky Way core | Rating |
|---|---|---|---|---|---|---|
| Jan | 10.2 h | 22 | — | — | — | Good |
| Feb | 10.0 h | 21 | — | — | 24° max | Good |
| Mar | 9.6 h | 21 | — | — | 35° max | Good |
| Apr | 8.6 h | 21 | — | — | 41° max | Good |
| May | 8.3 h | 20 | — | — | 41° max | Good |
| Jun | 7.5 h | 21 | — | — | 41° max | Good |
| Jul | 8.0 h | 21 | — | — | 41° max | Good |
| Aug | 8.5 h | 20 | — | — | 41° max | Good |
| Sep | 9.3 h | 20 | — | — | 37° max | Good |
| Oct | 9.9 h | 24 | — | — | 26° max | Good |
| Nov | 10.0 h | 23 | — | — | — | Good |
| Dec | 10.5 h | 25 | — | — | — | Good |
"Moon-free dark nights" counts nights with at least two hours of astronomical darkness during which the Moon stays below the horizon. "Clear nights" is the share of days in the ERA5 record averaging under 30% cloud cover.
Practical
What Mauna Kea is actually good for
- Exceptional seeing
- Both-hemisphere targets
- High-altitude transparency
For a decision on a specific night rather than a season, the SnapCosmos Night Engine scores tonight and the next six nights from these coordinates — . The method, weighting and known limits are documented on the Night Engine page, and its measured accuracy is published here.
FAQ
Common questions about the sky in Mauna Kea
- Can you see the Milky Way in Mauna Kea?
- Yes. Mauna Kea sits at Bortle 2 — excellent dark sky, where the Milky Way is an obvious, structured band whenever the galactic centre is above the horizon and the Moon is down.
- When is the best time of year to stargaze in Mauna Kea?
- It depends on what you want to see, and the month-by-month table on this page ranks every month by hours of astronomical darkness, moon-free nights and ten years of cloud statistics for these exact coordinates.
- How dark does it get in Mauna Kea?
- Mauna Kea is at latitude 19.8°N, and this page computes the hours of true astronomical darkness — Sun more than 18° below the horizon — for every month of the year at that latitude.
- Is tonight a good night in Mauna Kea?
- The SnapCosmos Night Engine scores tonight for these coordinates against the coming week using live cloud forecasts, Moon geometry and darkness, and returns a single go, wait or skip recommendation.
Where these numbers come from
- Ten-year cloud-cover climatology and historical night rankingERA5 reanalysisECMWF / Copernicus Climate Change Service
- Hourly cloud cover, precipitation, humidity and visibility forecastsOpen-Meteo forecast and archive APIOpen-Meteo
- Sun, Moon and planet positions, rise and set times, twilight phasesAstronomy Engine (VSOP87 / ELP2000 series)Don Cross, after the IMCCE and JPL analytical theories
- Bortle class and sky-brightness context for each locationWorld Atlas of Artificial Night Sky Brightness (Falchi et al., 2016)Science Advances / Light Pollution Map
- Definitions of civil, nautical and astronomical twilight, and lunar phase conventionsAstronomical Applications DepartmentUnited States Naval Observatory
Figures on this page last recomputed .
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