Japan astronomical observatory
Gekko Observatory
An astronomical observatory in Japan, and the real sky above it tonight.
Calculating the sky…
Drag to turn round. Stars from the HYG catalogue; glow and horizon from the light model and the terrain.
The place
Gekko Observatory.
Observatory
Gekko Observatory is an astronomical observatory in Japan, 312 m above the sea.
Its usual sky, with no Moon or clouds, is estimated at 20.19 mag/arcsec² — Bortle 5, suburban sky: the naked eye reaches stars of magnitude 5.6.
The nearest town of over 50,000 people is 7 km away.
The best months are from December to January: long dark nights and clearer skies.
The core of the Milky Way rises up to 26° above the horizon, and is up during the dark hours from March to September.
The relief hides 6% of the sky; the highest point of the horizon is 8° up, to the north-east.
Visit and sleep under the stars
- Visiting the observatoryMany observatories open for guided nights or open days: check the official site.Official site↗
- 富士箱根ランドplace to stay · 4.8 km · 115 within 10 km
- Kamizawanearest town · 4.6 km in a straight line
- Oshima Airport (OIM)nearest airport with scheduled flights · 51 km in a straight lineCar hire at HND airport (Tokyo)Discover Cars · sponsored link↗
Plan the night
A guided night, a bed nearby, a car.
Some links above are affiliate links: if you book through them we may earn a commission, at no extra cost to you. It never changes what the data on this page says.
The usual sky here
Bortle 5.
The Milky Way is faint, only overhead; the sky near the horizon is grey.
Our own rating, from verifiable data only: sky brightness (60 points), clear nights (25), open horizon (10) and altitude (5).
- 1Excellent dark sky≥ 21.89 · stars to mag 7.6
- 2Truly dark sky21.69–21.89 · stars to mag 7.1
- 3Rural sky21.25–21.69 · stars to mag 6.6
- 4Rural–suburban transition20.49–21.25 · stars to mag 6.1
- 5Suburban sky19.50–20.49 · stars to mag 5.6 You are here
- 6Bright suburban sky18.94–19.50 · stars to mag 5.1
- 7Suburban–urban transition18.38–18.94 · stars to mag 4.6
- 8City sky17.80–18.38 · stars to mag 4.1
- 9Inner-city sky< 17.80 · stars to mag 3.6
- 20.19Sky brightnessmag/arcsec² at the zenith — 21.9 is a natural sky
- 5.6Faintest starthe faintest magnitude the naked eye can see here
- 7 kmNearest big townover 50,000 people, in a straight line
- 312 mAltitudeabove the sea: less air and haze above you
- 94%Open skyof the half-sphere the relief leaves visible
Where the light comes from
The brightest glow on the horizon comes from Tokyo, 89 km to the north-east.
Each wedge is how much artificial light arrives from that direction (10° slices).
An estimate of the usual sky with no Moon and no clouds, from NASA's night-lights map and a light-propagation model (about ±0.3 mag). A given night depends on the Moon, the clouds, dust and humidity.
When to go
Best from December to January.
Hours of truly dark night, hours with the core of the Milky Way up, how often the sky is clear and the coldest night, month by month.
- 11h51%3°Jan
- 10h45%3°Feb
- 9.2h40%6°Mar
- 7.8h36%10°Apr
- 6.7h29%14°May
- 5.8h17%18°Jun
- 6.3h20%22°Jul
- 7.3h30%23°Aug
- 8.7h26%20°Sep
- 9.8h32%15°Oct
- 11h46%11°Nov
- 11h53%6°Dec
- Dark night (hours)
- Milky Way core up
- Clear sky
- Coldest night
- Best months
The Moon, night by night
A bright Moon washes out the faint stars. The highlighted nights are the dark ones (less than a quarter lit); below, the next new moons.
- 9 Nov2026
- 9 Dec2026
- 7 Jan2027
- 6 Feb2027
- 8 Mar2027
- 6 Apr2027
Night: Sun more than 18° below the horizon. Milky Way: the galactic centre more than 10° up during that night. Clear sky: 100 − NASA cloud amount (2001–2020). Coldest: average minimum brought to this altitude.
What happens in this sky
Meteors, eclipses, auroras.
Meteor showers
The next twelve months. The rate is what a dark sky shows with the radiant at its highest here; the Moon decides the rest.
- Orionidspeak 21 Oct 2026 · up to 19 meteors an hourMoon 69% lit at the peak
- Leonidspeak 17 Nov 2026 · up to 15 meteors an hourMoon 42% lit at the peak
- Geminidspeak 14 Dec 2026 · up to 150 meteors an hourMoon 18% lit at the peak
- Quadrantidspeak 4 Jan 2027 · up to 107 meteors an hourMoon 15% lit at the peak
- Lyridspeak 22 Apr 2027 · up to 18 meteors an hourMoon 99% lit at the peak
- Eta Aquariidspeak 6 May 2027 · up to 40 meteors an hourMoon 1% lit at the peak
- Southern Delta Aquariidspeak 30 Jul 2027 · up to 16 meteors an hourMoon 19% lit at the peak
- Perseidspeak 12 Aug 2027 · up to 92 meteors an hourMoon 74% lit at the peak
Eclipses
Lunar eclipses visible from here, and solar eclipses whose path crosses this country.
- Partial lunar eclipse6 july 2028Moon 13° up at mid-eclipse · 140 min
- Total lunar eclipse31 december 2028Moon 60° up at mid-eclipse · 71 min
- Partial lunar eclipse15 june 2030Moon 11° up at mid-eclipse · 143 min
- Total lunar eclipse25 april 2032Moon 41° up at mid-eclipse · 66 min
- Annular solar eclipse1 june 2030the path crosses this country — check the exact line before you go
- Total solar eclipse2 september 2035the path crosses this country — check the exact line before you go
Meteor dates: International Meteor Organization peaks. Lunar eclipses: computed (J. Meeus) and shown only when the Moon is above this horizon. Solar eclipses: Eclipse Predictions by Fred Espenak, NASA/GSFC (country on the path).
The horizon
360° around you.
The silhouette of the relief up to 30 km away (Copernicus DEM), with the light domes of the towns where they rise. Mountains are drawn taller than they are, to be seen.
Around, in OpenStreetMap
- 2observatories and planetariums within 30 km月光天文台, 箱根の里プラネタリウム
- 8viewpoints within 5 km坂公民館, 三島スカイウォーク, 西丹那駐車場 and 5 more
- 1named peaks within 5 km鷹ノ巣山
- 18car parks within 3 km
- 1campsites within 10 km
- 115places to stay within 10 km富士箱根ランド, スコーレプラザホテル, ドーミーイン三島 and 112 more
- 35restaurants and cafés within 5 km
- marked trails within 3 km
- shelters and huts within 5 km
- visitor centres within 5 km
- street lamps mapped within 2 km
Counted in OpenStreetMap, the map anyone can edit. A low number may just mean nobody has mapped it yet.
In our other atlases
Around it, by day.
The mountain, island, lake, beach or canyon this place is, and what else is nearby in the family's atlases.
Peakyas77 mountains within 25 km
Cavernyas1 caves within 20 km
Cascadyas11 waterfalls within 15 kmFigures from the sister sites' databases (Wikidata, HydroATLAS, GeoNames, OpenStreetMap). Links open when each site is online.
Photographs
By day and by night.
Other skies nearby.
Gekko Observatory
Japan
- 58Darkskyas Score
- 20.19Sky brightness
- 5Bortle
- 312 mAltitude
Nobeyama radio observatory
Japan · 102 km
- 72Darkskyas Score
- 21.26Sky brightness
- 3Bortle
- 1,350 mAltitude
Nihondaira Observatory
Japan · 51 km
- 44Darkskyas Score
- 19.17Sky brightness
- 6Bortle
- 303 mAltitude
Where these figures come from
| Name, type, certification | Wikidata (Q1499172) · CC0 |
|---|---|
| Sky brightness | NASA Earth Observatory, Black Marble 2016 (Suomi NPP VIIRS) · Darkskyas light model (Walker's law, fitted to 18 measured sites) |
| Night, Moon, Milky Way, stars | J. Meeus, Astronomical Algorithms · HYG v4.4 · Stellarium modern_iau (CC BY-SA 4.0) |
| Horizon and altitude | Copernicus DEM GLO-90 / GLO-30 · © DLR e.V., © Airbus Defence and Space GmbH, Copernicus/ESA |
| Clouds and temperature | NASA POWER (CERES SYN1deg, 2001–2020; MERRA-2) |
| Solar eclipses | Eclipse Predictions by Fred Espenak, NASA/GSFC |
| What is around | © OpenStreetMap contributors · ODbL |
| Images | EOX Sentinel-2 cloudless 2016 · CC BY 4.0; Wikimedia Commons |
| Sister atlases | Peakyas, Islandyas, Lakeyas, Cavernyas, Cascadyas |
Every figure is an average, an estimate or a count from a public dataset. Licences and methods: data sources.
The family
Do you prefer beaches, lakes, mountains, waterfalls, islands, rivers, canyons, caves, dark skies, viewpoints, birdwatching or forests?
Same idea, other landscapes: field atlases built on open data, in seven languages.
beaches
Find your beach: sea temperature, sun and swimming month by month.Visit 
lakes
Every lake on Earth: water temperature, ice, depth and the shore.Visit mountains
Every summit in 3D: summit weather, the 0 °C line, huts and trails.Visit waterfalls
Every waterfall: height, flow month by month and when it roars.Visit 
islands
Every island from the sea up: size, sea temperature, ferries and 3D.Visit 
rivers
Every river from source to sea: the journey, the flow and the basin in numbers.Visit 
canyons
Every canyon cut to scale: depth to the floor, rim and floor temperatures, trails and viewpoints.Visit caves
Every cave with its real depth and length: the rock above, the temperature inside all year, and how to visit.Visit 
dark skies
Where the night is still dark: the sky of every place, the Milky Way month by month, the Moon, eclipses and auroras.You are here
viewpoints
Every viewpoint with its real 360° panorama: the peaks you can name, how far you see and where the sun sets.Coming soonVisit 
birdwatching
Every bird sanctuary and wetland with the species recorded month by month: who is resident, who comes for the summer, who only passes through.Coming soonVisit 
forests
Every forest with its land-cover rings, what grows and lives in it, and the best months to walk it.Coming soonVisit