Light pollution maps and the Bortle scale.

What is a light pollution map?

Light pollution is artificial light that brightens the night sky and makes faint objects harder to see. Maps help you identify areas with less artificial light, but different maps may represent different measurements or models.

Noctis uses satellite-based nighttime light data in supported regions. The satellite measures light leaving the ground; that is different from directly measuring the sky above an observer. Use the map to compare candidates for a trip.

What does the Bortle scale mean?

The Bortle scale describes night-sky conditions using nine classes: class 1 is the darkest end and class 9 represents a heavily light-polluted city sky. Lower numbers indicate darker skies.

Noctis converts satellite radiance into an estimated Bortle level using a heuristic. This is a planning estimate, not a ground observation or a calibrated sky-brightness measurement. Two places with the same estimate can still offer different views on the night you visit.

How to compare two places in Noctis

1. Select a location in a supported region and inspect its reading.
2. Use Compare to keep that location as a reference.
3. Select another candidate and review the difference.
4. Check access and use the planner for your chosen date.

Compare locations that fit your trip. A small improvement nearby may be useful for a quick outing; a longer journey needs more planning. No single map reading can make that decision for you.

What a map cannot tell you

The light pollution layer is not a live view of tonight’s sky. It cannot confirm that a site is open, that a local lamp has been switched off or that the weather will cooperate. Use local information and the relevant forecast alongside the map.

Coverage is regional, not worldwide. Open Data & coverage in Noctis to inspect the included regions. Missing data is not a Bortle 1 reading. The illustrative sky view is also a visual explanation, not a prediction of exactly what your eyes or camera will see.