How dark is the sky in Castile and León?
Sky darkness for 19 towns and parks in Castile and León, worked out from NASA satellite images of light at night (2025). 10 of them have skies of Bortle 4 or darker, where the Milky Way shows overhead. The darkest is Montaña Palentina Natural Park (21.64, Bortle 4), the brightest Burgos (18.55, Bortle 7). Milky Way season in Castile and León runs April to August: on moonless nights the bright core stands clear of the horizon, climbing to about 21° at its highest.
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 Castile and León
- Montaña Palentina Natural ParkBortle 421.64
- Picos de Europa National ParkBortle 421.62
- Lagunas de Neila Natural ParkBortle 421.56
- the Sierra de GredosBortle 421.56
- Cañón del Río Lobos Natural ParkBortle 421.53
Among the places on this site. Plenty of land between them is just as dark, with no town or park to name it by.