BORTLE CLASS 9 / SKY KEY
Inner-city sky
The bright end of the scale, where only the brightest stars and solar-system objects stand out easily.
9
HOW TO READ IT
One number is a sketch of the sky, not the whole night.
A Bortle class describes what the sky looks like under particular conditions. Walk across a large park, turn toward a town, add snow or smoke, and the view can change. Use the number to compare darkness quickly, then read the stop page for the horizon, headlights, access and everything else that decides whether the place actually works.
Colorado stops currently logged as Bortle 9
No stop is carrying this number yet. That is fine. The box stays empty until there is enough field or source information to defend the rating.