How dark is the sky where you'll be? Enter coordinates or use your location to get an estimated Bortle class, zenith sky brightness in mag/arcsec² and the faintest stars you could see — plus the towns contributing most of the glow.
The estimate uses Walker's law with U.S. town populations, calibrated against known dark-sky sites. It ignores terrain and local lighting, so treat it as a planning guide.
How to use the Light Pollution Checker
- Enter or detect a location.
- Read the Bortle class and SQM estimate.
- Check which towns cause the glow — and in which direction.
FAQ
What Bortle class do I need for the Milky Way?
Class 4 or darker shows the Milky Way well; classes 1–3 show rich detail.
Why is my reading different from a light pollution map?
Satellite maps measure upward light; this model estimates sky glow from population. Both are approximations.
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