Finland astronomical observatory
Iso-Heikkilä Observatory
An astronomical observatory in Finland, 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
Iso-Heikkilä Observatory.
Astronomical observatory in Turku, Finland
Iso-Heikkilä Observatory is an astronomical observatory in Finland.
Its usual sky, with no Moon or clouds, is estimated at 17.82 mag/arcsec² — Bortle 8, city sky: the naked eye reaches stars of magnitude 3.8.
The nearest town of over 50,000 people is 2 km away.
The best months are in October and from December to March: long dark nights and clearer skies.
Auroras come a few times a year, with storms of Kp 3.2 or more.
The horizon is open all round: nothing in the relief rises more than 3°.
Visit and sleep under the stars
- Visiting the observatoryMany observatories open for guided nights or open days: check the official site.Official site↗
- Raision matkaparkkicampsite · 6.3 km · 7 within 10 km
- Harrietplace to stay · 1.4 km · 44 within 10 km
- Iso-Heikkilänearest town · 0.6 km in a straight line
- Turku Airport (TKU)nearest airport with scheduled flights · 7 km in a straight lineCar hire at TMP airport (Tampere / Pirkkala)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 8.
The sky is orange or white; you can read by it; only the brightest stars show.
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
- 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 You are here
- 9Inner-city sky< 17.80 · stars to mag 3.6
- 17.82Sky brightnessmag/arcsec² at the zenith — 21.9 is a natural sky
- 3.8Faintest starthe faintest magnitude the naked eye can see here
- 2 kmNearest big townover 50,000 people, in a straight line
- 20 mAltitudeabove the sea: less air and haze above you
- 99%Open skyof the half-sphere the relief leaves visible
Where the light comes from
The brightest glow on the horizon comes from Kaarina, 9 km to the south-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 in October and from December to March.
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.
- 12h17%-7°Jan
- 10h21%-8°Feb
- 7.5h30%-5°Mar
- 2.5h33%0°Apr
- 0h38%5°May
- 0h36%10°Jun
- 0h36%13°Jul
- 0h36%12°Aug
- 6.0h33%8°Sep
- 9.2h23%3°Oct
- 11h14%0°Nov
- 13h16%-4°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 14 meteors an hourMoon 72% lit at the peak
- Leonidspeak 17 Nov 2026 · up to 12 meteors an hourMoon 46% lit at the peak
- Geminidspeak 14 Dec 2026 · up to 133 meteors an hourMoon 21% lit at the peak
- Quadrantidspeak 4 Jan 2027 · up to 108 meteors an hourMoon 12% lit at the peak
- Lyridspeak 22 Apr 2027 · up to 16 meteors an hourMoon 98% lit at the peak
- Eta Aquariidspeak 6 May 2027 · up to 24 meteors an hourMoon 0% lit at the peak
- Perseidspeak 12 Aug 2027 · up to 100 meteors an hourMoon 77% lit at the peak
Eclipses
Lunar eclipses visible from here, and solar eclipses whose path crosses this country.
- Partial lunar eclipse12 january 2028Moon 23° up at mid-eclipse · 53 min
- Total lunar eclipse31 december 2028Moon 22° up at mid-eclipse · 71 min
- Total lunar eclipse20 december 2029Moon 52° up at mid-eclipse · 53 min
- Total lunar eclipse18 october 2032Moon 29° up at mid-eclipse · 46 min
Auroras
Auroras come with geomagnetic storms (Kp 3.2 or more), a few times a year, low on the horizon. Dark months: from September to April.
- 0quiet
- 1
- 2
- 3active
- 4
- 5storm
- 6
- 7strong
- 8
- 9extreme
Estimate from the geomagnetic latitude (dipole model) and NOAA's oval boundaries. Watch the live Kp forecast before going out.
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 kmIso-Heikkilän tähtitorni, Tuorlan Planetaario
- 22viewpoints within 5 kmOptisen lennättimen muistomerkki and 21 more
- 87named peaks within 5 kmYliopistonmäki, Vartiovuori, Puolalanmäki and 84 more
- 9marked trails within 3 kmEuroopan vapaareititetty digitaalinen kävelyreitti E6, Suomi, Kuhankuonon retkeilyreitistö, Aurajoenrannan ulkoilupolku and 6 more
- 240shelters and huts within 5 km
- 2,471car parks within 3 km
- 7campsites within 10 kmRaision matkaparkki, Y-Hovi, Ruissalo Camping and 4 more
- 44places to stay within 10 kmHarriet, Park Hotel, Omena-hotelli Turku Humalistonkatu and 41 more
- 2visitor centres within 5 kmVisit Turku, Myllärintalo
- 365restaurants and cafés within 5 km
- 1,328street 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.
Peakyas23 mountains within 25 km
Coastya12 beaches within 10 km
Lakeyas4 lakes within 15 km
Cavernyas1 caves within 20 kmFigures from the sister sites' databases (Wikidata, HydroATLAS, GeoNames, OpenStreetMap). Links open when each site is online.
Other skies nearby.
Iso-Heikkilä Observatory
Finland
- 23Darkskyas Score
- 17.82Sky brightness
- 8Bortle
- 20 mAltitude
Tuorla Observatory
Finland · 12 km
- 44Darkskyas Score
- 19.38Sky brightness
- 6Bortle
- 60 mAltitude
Where these figures come from
| Name, type, certification | Wikidata (Q2976682) · 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, Coastya, Lakeyas, Cavernyas |
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