/sky lp
/sky lp [location] [remember]
How dark the sky is, straight overhead, at a location – an estimate from David Lorenz’s light pollution model, in magnitudes per square arcsecond, where a HIGHER number means a DARKER sky (a natural, unpolluted sky is about 22.0; a big city is around 17 or less).
Usage: /sky lp location: Flagstaff, AZ — or just /sky lp
with a saved default location. Add remember: True to also save
the typed location as your new default.
The reading comes from David Lorenz’s Light Pollution Atlas 2025, a model that turns satellite night-light data into an estimate of zenith sky brightness at roughly 1 km resolution: modeled, not measured on the ground. From that modeled magnitude the command also works out the atlas’s Light Pollution Zone (0 is the darkest, 7b the brightest) and how many times brighter than a natural sky it is, and says that those are derived from it. It is zenith brightness, not a Bortle class, and not a whole-sky average. A link to lightpollutionmap.app is included for comparing against that site’s own numbers; it is centered on the general area (rounded to about 10 km), never your exact coordinates.
The reading comes with a wide map of the surrounding ~300 km, colored by the atlas’s zones, with coastlines, rivers and a few nearby towns drawn in for orientation and dashed rings at 50 and 100 km for scale. A solid ring marks your general area. The map is centered on coordinates rounded to about 10 km, and the ring is sized to always contain your real position, so it never pinpoints you; no coordinates or axes appear anywhere on it. If the map can’t be drawn for some reason, you still get the reading.
The atlas covers latitudes from about 65°S to 75°N. Anywhere else the command says so instead of guessing.
Parameters
| Name | Required | Description |
|---|---|---|
location | No | City name, decimal, or DMS coordinates. Leave blank to use your saved default. |
remember | No | Also save this as your new default location (otherwise this is a one-off lookup) |