# USNO Astronomical Applications API

Category: [Weather forecasts](https://free-web-services.com/web-services/geo/weather/)  
Page: https://free-web-services.com/web-services/geo/weather/usno-astronomical-applications-api.html  
Documentation: https://aa.usno.navy.mil/data/api

The Astronomical Applications API of the US Naval Observatory gives sun and moon data for any place and date: rise, set and transit times, twilight, moon phase and illumination. Other endpoints list the moon phases of a year, equinoxes and solstices, solar eclipses, daylight saving time dates, sidereal time and Julian dates. Requests are plain GET calls that return JSON or GeoJSON. Free, no key needed.

- API key: Not needed
- Pricing: Free, no key needed.
- From the browser: Yes (CORS)
- Formats: JSON
- Interface: REST, HTTP-GET
- Provider: aa.usno.navy.mil

Example request:

```sh
curl 'https://aa.usno.navy.mil/api/rstt/oneday?date=2026-11-01&coords=51.5,-0.12'
```

The JavaScript works in a web page as well as in Node.js 18 or newer.