Sky Tonight
Plan tonight with local twilight, darkness, Moon phase, and observing conditions.
How to use this tracker
Astronomical darkness begins when the Sun is 18° below the horizon. A bright Moon can reduce visibility of faint objects.
Sky Tonight is a planning tool for deciding when your local sky is likely to be darkest. It calculates solar altitude, twilight crossings, the remaining or next darkness window, approximate Moon phase and illumination, and a simple observing score for your location.
How to plan your observing session
Set your location first. The tool then calculates local twilight and darkness from the Sun’s position rather than relying on a fixed clock time. That matters because sunset and astronomical darkness change with season, latitude and longitude.
Moon illumination is also useful context: a bright Moon can wash out faint stars, meteors and deep-sky objects even when the Sun is well below the horizon. The observing score combines these basic astronomical conditions into a quick planning signal.
What this tool does not forecast
Sky Tonight is not a weather model. It does not measure cloud cover, transparency, humidity, smoke or local light pollution. A high darkness score can therefore coincide with poor weather. Check a trusted local weather service before traveling to an observing site.
Use it with live space tools
Pair this page with Meteor Shower Tracker to judge Moon and darkness conditions near a shower peak, with Aurora Forecast Tonight for geomagnetic activity, or with Satellites Above Me Tonight for orbital passes.
Further skywatching guidance
NASA’s Skywatching pages provide observing guides, monthly highlights and background information on common night-sky events.