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Estimated from VIIRS night-lights radiance — a comparison tool, not an on-site sky-quality measurement.
The glowing layer is NASA VIIRS Black Marble — a cloud-free composite of the Earth's surface at night, from the 2016 annual edition, the most recent global composite NASA publishes on GIBS. City light patterns change slowly, so it remains representative — but a brand-new suburb or highway may not glow here yet. Every bright patch is artificial light escaping upward: cities, highways, greenhouses, gas flares, fishing fleets. The darker the map, the more stars you will see.
…
Best stargazing nights (new Moon):
1. Get at least 30–50 km from the nearest big city — light domes reach far beyond
the city edge.
2. Go around the new Moon (dates on the left) — a full Moon is nature's
own light pollution.
3. Give your eyes 20–30 minutes without any white light — one
phone screen resets the clock.
| Class | Sky | What you can see |
|---|---|---|
| 1 | Excellent dark site | The Milky Way casts visible shadows; zodiacal light is obvious; M33 with the naked eye. |
| 2 | Truly dark | Summer Milky Way is richly structured; airglow visible on the horizon. |
| 3 | Rural sky | Milky Way still complex; some light domes low on the horizon. |
| 4 | Rural / suburban edge | Milky Way clearly visible overhead but washed out lower; light domes in several directions. |
| 5 | Suburban | Only the brighter parts of the Milky Way survive; the sky is visibly grey near the horizon. |
| 6 | Bright suburban | Milky Way barely traceable near the zenith on the best nights. |
| 7 | Suburban/urban transition | Milky Way invisible; the whole sky has a greyish glow; brighter deep-sky objects only in telescopes. |
| 8–9 | City / inner city | Only the Moon, planets and the brightest stars; many constellations unrecognizable. |
It answers, it doesn't just display. Most light-pollution maps show you a colored overlay and leave the interpretation to you. Here you click, and get a plain-language answer: the estimated Bortle class, what that means for the Milky Way, and — with the 🌌 Find darkest nearby button — where to drive for a darker sky, based on the same satellite data.
It is honest about its limits. Satellites measure light emitted upward from the ground, not the brightness of the sky you look through. Atmosphere, humidity and distant light domes shift the real Bortle class — which is why every estimate on this page says estimate. For a definitive reading, amateur astronomers use an SQM meter on site.
Nothing about you leaves this page. The tiles come from our own EU servers and NASA's public imagery; your location, if you share it, is used in your browser only.
It is computed from VIIRS Black Marble night-lights radiance — how much light the ground sends up. It is reliable for comparing locations and finding darker areas; the exact class on a given night also depends on the atmosphere and on light domes from cities beyond the horizon. Treat ±1 class as the honest error bar — and note that bright bare surfaces (deserts, fresh snow) reflect enough light in the composite to read 1–2 classes worse than they really are.
In most of Europe and the eastern U.S., a weekend trip can get you to class 3–4; class 1–2 needs remote regions — high deserts, oceans, far northern latitudes. Use the darkest-nearby finder above: even dropping two classes transforms what you can see.
Yes — a full Moon brightens the sky by several magnitudes and can make a Bortle 2 site perform like a suburb. Plan deep-sky observing within ~5 days of a new Moon; the dates are listed above.
NASA VIIRS Black Marble (public domain, via NASA GIBS), GeoNames city database (CC BY 4.0), and our own Tilezza base map tiles. The Bortle mapping is our own calibration and is labeled as an estimate.
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