How dark is the sky in Alaska?
Sky darkness for 25 towns and parks in Alaska, worked out from NASA satellite images of light at night (2025). 23 of them have skies of Bortle 4 or darker, where the Milky Way shows overhead. The darkest is Bering Land Bridge National Preserve (21.95, Bortle 2), the brightest Anchorage (17.70, 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
Darkest skies in Alaska
- Bering Land Bridge National PreserveBortle 221.95
- Gates of the Arctic National Park and PreserveBortle 221.95
- Glacier Bay National Park and PreserveBortle 221.95
- Kobuk Valley National ParkBortle 221.95
- Noatak National PreserveBortle 221.95
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 Alaska
All 25 places in Alaska
Amber names are parks and certified dark-sky places. The figure is the Bortle class: 1 darkest, 9 city center.
Admiralty Island National Monument2Afognak Island State Park2Alaska Chilkat Bald Eagle Preserve2Aleutian Islands World War II National Monument5Anchorage8Aniakchak National Monument3Aniakchak National Preserve3Bering Land Bridge National Preserve2Cape Krusenstern National Monument2Chugach National Forest3Denali National Park and Preserve2Denali State Park2Gates of the Arctic National Park and Preserve2Glacier Bay National Park and Preserve2Kachemak Bay State Park4Katmai National Park and Preserve4Kenai Fjords National Park4Kobuk Valley National Park2Misty Fiords National Monument2Noatak National Preserve2Tongass National Forest3White Mountains National Recreation Area3Wood-Tikchik State Park2Wrangell-St. Elias National Park and Preserve2Yukon-Charley Rivers National Preserve2