YozoraAtlas

How dark is the sky in South Dakota?

Sky darkness for 8 towns and parks in South Dakota, worked out from NASA satellite images of light at night (2025). 6 of them have skies of Bortle 4 or darker, where the Milky Way shows overhead. The darkest is Badlands National Park (21.79, Bortle 3), the brightest Sioux Falls (17.63, 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

NASA satellite night-lights map of South Dakota with every place marked

Darkest skies in South Dakota

  1. Badlands National ParkBortle 321.79
  2. Fossil Cycad National MonumentBortle 321.76
  3. Jewel Cave National MonumentBortle 321.70
  4. Wind Cave National ParkBortle 421.65
  5. Black Hills National ForestBortle 421.54

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 Dakota

  1. Sioux FallsBortle 817.63
  2. Rapid CityBortle 817.88

All 8 places in South Dakota

Amber names are parks and certified dark-sky places. The figure is the Bortle class: 1 darkest, 9 city center.
Badlands National Park3Black Hills National Forest4Custer State Park4Fossil Cycad National Monument3Jewel Cave National Monument3Rapid City8Sioux Falls8Wind Cave National Park4