How dark is the sky in the United Kingdom?
Sky darkness for 299 towns and parks in the United Kingdom, worked out from NASA satellite images of light at night (2025). 92 of them have skies of Bortle 4 or darker, where the Milky Way shows overhead. The darkest is North Uist (21.94, Bortle 2), the brightest London (16.97, Bortle 8).
19
Bortle class, 1 pristine to 9 city center
park or dark-sky place
city
Numbers like 21.95 or 16.97 are the brightness of the sky overhead on a clear, moonless night, in mag/arcsec². The scale runs backwards: a lower number means a brighter sky, from about 22 for a natural sky to about 17 in a city center.
How the readings are made
Darkest skies in the United Kingdom
- North UistScotland · Bortle 221.94
- South UistScotland · Bortle 221.92
- AssyntScotland · Bortle 221.91
- TireeScotland · Bortle 221.90
- CollScotland · Bortle 321.89
Among the places on this site. Plenty of land between them is just as dark, with no town or park to name it by.
Darkest place in each nation of the United Kingdom
| Nation | Places | Dark places Bortle 1 to 4 | Darkest place |
|---|---|---|---|
| England | 217 places | 35 dark | the Isles of Scilly21.87 · Bortle 3 |
| Northern Ireland | 13 places | 7 dark | the Sperrins21.34 · Bortle 4 |
| Scotland | 49 places | 38 dark | North Uist21.94 · Bortle 2 |
| Wales | 20 places | 12 dark | Coed y Bont21.55 · Bortle 4 |