YozoraAtlas

How dark is the sky in Friesland?

Sky darkness for 3 towns and parks in Friesland, worked out from NASA satellite images of light at night (2025). 2 of them have skies of Bortle 4 or darker, where the Milky Way shows overhead. The darkest is Boschplaat (21.66, Bortle 4), the brightest Leeuwarden (19.68, Bortle 5). The bright core of the Milky Way never climbs clear of the horizon haze anywhere in Friesland while the sky is fully dark; the rest of the band passes overhead, with the longest moonless nights from September to March.

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

NASA satellite night-lights map of Friesland with every place marked

Darkest skies in Friesland

  1. BoschplaatBortle 421.66
  2. De Alde Feanen National ParkBortle 421.02

Among the places on this site. Plenty of land between them is just as dark, with no town or park to name it by.

Brightest city skies in Friesland

  1. LeeuwardenBortle 519.68

All 3 places in Friesland

Amber names are parks and certified dark-sky places. The figure is the Bortle class: 1 darkest, 9 city center.
Boschplaat4De Alde Feanen National Park4Leeuwarden5