DarkSkyCheck Measures the Night Sky City by City

Field notes

DarkSkyCheck converts NOAA VIIRS radiance readings into six descriptive bands rather than presenting them as Bortle classes. Its coverage is limited to incorporated US cities of at least 10,000 people, and the homepage explicitly says it cannot represent true wilderness darkness at backyard-level resolution. City pages add a nearest darker city and straight-line distance, while noting that actual driving routes will be longer.