YozoraAtlas

How dark is the sky in Wyoming?

Sky darkness for 15 towns and parks in Wyoming, worked out from NASA satellite images of light at night (2025). 13 of them have skies of Bortle 4 or darker, where the Milky Way shows overhead. The darkest is Yellowstone National Park (21.90, Bortle 2), the brightest Cheyenne (18.31, 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 Wyoming with every place marked

Darkest skies in Wyoming

  1. Yellowstone National ParkBortle 221.90
  2. Shoshone National ForestBortle 321.89
  3. Grand Teton National ParkBortle 321.86
  4. Bridger National ForestBortle 321.83
  5. Devils Tower National MonumentBortle 321.78

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 Wyoming

  1. CheyenneBortle 818.31
  2. CasperBortle 718.47

All 15 places in Wyoming

Amber names are parks and certified dark-sky places. The figure is the Bortle class: 1 darkest, 9 city center.
Bridger National Forest3Bridger-Teton National Forest4Casper7Cheyenne8Devils Tower National Monument3Fort Bridger4Fort Fred Steele State Historic Site4Fossil Butte National Monument3Glendo State Park3Grand Teton National Park3Hot Springs State Park4Medicine Bow-Routt National Forest3Shoshone Cavern National Monument4Shoshone National Forest3Yellowstone National Park2