Guides

• How DarkSkyCheck Measures Your City's Night Sky — The exact NOAA/EOG satellite dataset behind every city's brightness band, named and sourced, and why it is not a Bortle class.
• The Bortle Scale, and Why This Site Doesn't Report One — What the 9-point Bortle scale actually measures, how it differs from satellite radiance, and why the two agree most of the time but not always.
• Your Brightness Band Isn't the Whole Answer: When to Actually Look Up — Moon phase, weather, and the season all move what you'll see on a given night more than a small difference in brightness band ever will.
• What This Dataset Does and Doesn't Cover — Why this site only covers incorporated US cities of 10,000 or more, what "nearest darker sky" actually measures, and where the real limits are.