YozoraAtlas

How dark is the sky in South Savo?

Sky darkness for 4 towns and parks in South Savo, 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 Kolovesi National Park (21.74, Bortle 3), the brightest Mikkeli (18.78, Bortle 7). The bright core of the Milky Way never climbs clear of the horizon haze anywhere in South Savo while the sky is fully dark; the rest of the band passes overhead, with the longest moonless nights from October 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 South Savo with every place marked

Darkest skies in South Savo

  1. Kolovesi National ParkBortle 321.74
  2. Linnansaari National ParkBortle 421.68

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 South Savo

  1. MikkeliBortle 718.78
  2. SavonlinnaBortle 619.28

All 4 places in South Savo

Amber names are parks and certified dark-sky places. The figure is the Bortle class: 1 darkest, 9 city center.
Kolovesi National Park3Linnansaari National Park4Mikkeli7Savonlinna6