How dark is the sky in South Ostrobothnia?
Sky darkness for 2 towns and parks in South Ostrobothnia, worked out from NASA satellite images of light at night (2025). None of them have skies of Bortle 4 or darker, where the Milky Way shows overhead. The darkest is Lauhanvuori National Park (20.46, Bortle 5), the brightest Seinäjoki (17.84, Bortle 8). The bright core of the Milky Way never climbs clear of the horizon haze anywhere in South Ostrobothnia while the sky is fully dark; the rest of the band passes overhead, with the longest moonless nights from October to March.
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 South Ostrobothnia
Among the places on this site. Plenty of land between them is just as dark, with no town or park to name it by.