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App summary
iCSC — the Clear Sky Chart Viewer — is a free iOS app built for people who want the best conditions for observing the night sky. It displays Clear Sky Chart forecasts that help users plan sessions by showing many sky and weather variables for selected observing sites.
Forecast variables shown
The app reports a range of parameters used by amateur and serious observers alike:
- Darkness and sky brightness
- Atmospheric seeing quality
- Cloud coverage
- Air temperature and thermal information
- Humidity levels
- Wind conditions
- Transparency of the sky
Coverage and data sources
iCSC provides predictions for more than 4,600 observing locations across North America. Forecasts are generated from established meteorological models and trusted weather datasets to give reliable guidance for planning viewing sessions.
How to find and keep charts
Navigation and quick access are straightforward:
- Save commonly used charts to a favorites list for one-tap access
- Browse charts visually using the map interface
- Search or filter charts by site name or nearby location
Although its primary audience is astronomers, the app is equally useful for anyone who enjoys stargazing and wants an accurate short-term sky forecast.
Recommended free alternative
If you want another option, try RadarNow — a free weather radar app that many users pair with sky-forecast tools to track incoming clouds and precipitation in real time.
Technical
- iPhone
- Free
