United States astronomical observatory
Yerkes Observatory
An astronomical observatory in United States, 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
Yerkes Observatory.
Astronomical observatory in Wisconsin, USA
Yerkes Observatory is an astronomical observatory in United States, 334 m above the sea.
Its usual sky, with no Moon or clouds, is estimated at 20.33 mag/arcsec² — Bortle 5, suburban sky: the naked eye reaches stars of magnitude 5.7.
The nearest town of over 50,000 people is 40 km away.
The best months are in September: long dark nights and clearer skies.
The core of the Milky Way rises up to 18° above the horizon, and is up during the dark hours from April to August.
Auroras are rare, needing storms of Kp 6.7 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↗
- House in the Woodcampsite · 7.2 km · 2 within 10 km
- Lakefront Cottageplace to stay · 0.4 km · 48 within 10 km
- Williams Baynearest town · 1.6 km in a straight line
- Chicago Rockford International Airport (RFD)nearest airport with scheduled flights · 61 km in a straight lineCar hire at MKE airport (Milwaukee)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
- 20.33Sky brightnessmag/arcsec² at the zenith — 21.9 is a natural sky
- 5.7Faintest starthe faintest magnitude the naked eye can see here
- 40 kmNearest big townover 50,000 people, in a straight line
- 334 mAltitudeabove the sea: less air and haze above you
- 100%Open skyof the half-sphere the relief leaves visible
Where the light comes from
The brightest glow on the horizon comes from Chicago, 109 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 September.
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.
- 11h33%-12°Jan
- 10h35%-11°Feb
- 8.8h36%-4°Mar
- 7.2h38%1°Apr
- 5.3h36%8°May
- 4.2h44%14°Jun
- 4.7h52%17°Jul
- 6.7h52%16°Aug
- 8.3h53%11°Sep
- 9.8h40%4°Oct
- 11h36%-2°Nov
- 12h29%-8°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 18 meteors an hourMoon 75% lit at the peak
- Leonidspeak 17 Nov 2026 · up to 14 meteors an hourMoon 49% lit at the peak
- Geminidspeak 14 Dec 2026 · up to 148 meteors an hourMoon 23% lit at the peak
- Quadrantidspeak 4 Jan 2027 · up to 109 meteors an hourMoon 11% lit at the peak
- Lyridspeak 22 Apr 2027 · up to 18 meteors an hourMoon 97% lit at the peak
- Eta Aquariidspeak 6 May 2027 · up to 36 meteors an hourMoon 0% lit at the peak
- Southern Delta Aquariidspeak 30 Jul 2027 · up to 13 meteors an hourMoon 13% lit at the peak
- Perseidspeak 12 Aug 2027 · up to 96 meteors an hourMoon 80% lit at the peak
Eclipses
Lunar eclipses visible from here, and solar eclipses whose path crosses this country.
- Partial lunar eclipse12 january 2028Moon 60° up at mid-eclipse · 53 min
- Total lunar eclipse26 june 2029Moon 15° up at mid-eclipse · 101 min
- Total lunar eclipse20 december 2029Moon 3° up at mid-eclipse · 53 min
- Total solar eclipse30 march 2033the path crosses this country — check the exact line before you go
Auroras
Auroras are rare: only strong storms (Kp 6.7+) bring them this far, a few times per solar cycle.
- 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
- 4observatories and planetariums within 30 kmYerkes Observatory, Yerkes Sun Telescope, Observatory and 1 more
- 2viewpoints within 5 kmLake Geneva Club Historical Gazebo
- 1marked trails within 3 kmLake Geneva Shore Path
- 8shelters and huts within 5 kmLake Geneva Club Historical Gazebo, Lions Field House and 6 more
- 34car parks within 3 km
- 2campsites within 10 kmHouse in the Wood, Lake Geneva Youth Camp
- 48places to stay within 10 kmLakefront Cottage, Belfry House, The Ridge Hotel and Spa and 45 more
- 24restaurants and cafés within 5 km
- 46street lamps mapped within 2 km
- named peaks within 5 km
- visitor centres within 5 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.
Peakyas2 mountains within 25 km
Lakeyas4 lakes 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.
Yerkes Observatory
United States
- 61Darkskyas Score
- 20.33Sky brightness
- 5Bortle
- 334 mAltitude
Beverly Shores
United States · 163 km
- 56Darkskyas Score
- 20.07Sky brightness
- 5Bortle
- 189 mAltitude
Adler Planetarium
United States · 111 km
- 20Darkskyas Score
- 17.64Sky brightness
- 9Bortle
- 184 mAltitude
Goethe Link Observatory
United States · 382 km
- 56Darkskyas Score
- 19.97Sky brightness
- 5Bortle
- 293 mAltitude
Where these figures come from
| Name, type, certification | Wikidata (Q14310) · 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, Lakeyas |
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