Astrophotography planning
Dark Sky Calendar
Find the nights when moonlight stays out of your way, astronomical darkness lasts longest, and the Milky Way core is well placed for your location. Compare sites with the estimated Bortle light-pollution layer.
Selected observing location
Half Moon Bay, CA, United States
37.464° N, 122.429° W · America/Los Angeles
Choose a location
Preparing the calendar…
A night is dark when the Moon is below the horizon for most astronomical darkness, or is less than 20% illuminated.
Choose a date to compare moonlight and darkness around the world.
Drag to pan, scroll or pinch to zoom, and click to inspect a location.
How the calendar scores a night
The planner samples the Sun, Moon, and Milky Way core every five minutes. It uses astronomical darkness when the Sun reaches 18° below the horizon, falling back to nautical darkness at high latitudes. Green nights are mostly moon-free or have a Moon under 20% illumination.
What the map can—and cannot—tell you
The Bortle layer is an estimate derived from satellite-observed nighttime lights, not an on-site sky-quality measurement. The calendar is not a weather forecast, and times assume a flat, sea-level horizon. Check clouds, smoke, local terrain, and site access before traveling.
Astronomical calculations follow Jean Meeus, Astronomical Algorithms. Time-zone boundaries use tz-lookup (CC0); land data is from Natural Earth via world-atlas; place data © GeoNames (CC BY 4.0) via all-the-cities. Light-pollution bands are derived from NASA Earth Observatory Black Marble 2016 imagery. Location searches and calculations run in your browser. Coordinates are stored only in your browser unless you explicitly copy a share link.