How dark is your sky?
An estimate from the world atlas of light pollution: how bright the night sky is above your place, what that glow hides, where the nearest darker sky is — and where on Earth the Milky Way still shows.
Working it out…
What this sky shows
Darker skies, near and far
Light pollution hides the Milky Way from more than a third of humanity, including 60% of Europeans and nearly 80% of North Americans (Falchi et al., 2016).
Drag to move, pinch or scroll to zoom, tap any place for its sky. Up close, each square is about 5 km.
Where the glow comes from
Towns light up the sky above them, and the glow spreads for tens of kilometres: low in their direction the sky is brighter and fewer stars show. If you see only part of the sky from home, My view shows these light domes over your compass.
How this is worked out
The artificial sky brightness comes from the New World Atlas of Artificial Night Sky Brightness (Falchi et al., 2016), computed from 2014 satellite images of the night lights. StarsMenu averages it over cells about 5 km across. Adding the natural sky glow gives the brightness at the zenith in magnitudes per square arcsecond — the number a Sky Quality Meter reads. From it come an approximate Bortle class and the faintest stars you can see with dark-adapted eyes (7.93 − 5·log₁₀(104.316 − SQM/5 + 1)).
On the map, the Milky Way counts as visible where the artificial brightness is below 688 μcd/m², about four times the natural glow of the night sky: in the atlas, that is the level of light above which the Milky Way is no longer visible. Far out, the map shows cells of 0.15° (about 15 km) averaged from the 5 km ones.
It is an estimate: lighting has grown since 2014, especially with white LEDs; a streetlight next to you, the Moon, haze and your eyes all change what you actually see. The light domes add the glow of every cell within 200 km, weighted by distance to the power −2.5 (Walker’s law).
Sources and credits
Coastlines and lakes for the light pollution map: Natural Earth (public domain).