Reference · built on requestCommons signalPlaces & geographic reference

USNO Astronomical Applications API

Sunrise, sunset, civil twilight, moon phases, and solar position for any date and coordinates from the US Naval Observatory.

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About

The US Naval Observatory Astronomical Applications Department provides celestial calculations and reference data. Its public REST API computes precise astronomical phenomena for any geographic coordinate pair and calendar date, including sunrise, sunset, civil, nautical, and astronomical twilight times, moonrise and moonset, lunar phase fractions, and solar and lunar altitude and azimuth angles.

Through Fibric, an operator references solar elevation and twilight schedules for facility locations, proposing automated exterior lighting schedules or daylight harvesting adjustments for building systems.

This is a reference listing. It documents what Fibric would read from USNO Astronomical Applications API and what it could propose, based on the publisher's published interfaces. Fibric builds it under a managed deployment when you request it; selecting it here installs nothing.

Inputs

  • Daily solar and lunar rise, set, and transit times via GET /api/rstt/oneday
  • Civil, nautical, and astronomical twilight start and end times for specific coordinates
  • Moon phase names, phase dates, and fraction of lunar disk illuminated from GET /api/moon/phase
  • Solar and lunar coordinates, altitude, and azimuth via GET /api/celnav
  • Equinox and solstice dates and earth season start times from GET /api/seasons

Proposed actions

Read-only. This feed informs operators; it changes nothing.

Proposed actions are target capabilities. Every action runs propose-first and needs a validated deployment and the appropriate permissions.

What you can build

  • Automate exterior perimeter lighting schedules

    Calculate exact civil twilight end and start times across facility portfolios, proposing optimized outdoor security lighting schedules to save energy.

    With Daylight Dimming, Peak Demand

  • Optimize daylighting controls in commercial spaces

    Track daily solar altitude and azimuth angles for building orientations, proposing blind positioning adjustments to minimize glare and cooling loads.

    With Daylight Dimming, Guest Comfort

  • Schedule daylight-dependent field service calls

    Incorporate sunset times into technician route schedules, proposing dispatch sequences that ensure outdoor rooftop service calls conclude before dusk.

    With Field Dispatch

Requirements

  • Target date formatted as YYYY-MM-DD or split into year, month, and day parameters
  • Latitude and longitude coordinates formatted in decimal degrees (e.g., coords=38.92,-77.07)
  • Timezone offset parameter (tz) or handling of coordinated universal time results
Authentication
None. The US Naval Observatory Astronomical Applications API is a public US Government web service requiring no authentication or API keys.

Limits

  • The API generates ephemeris calculations dynamically on request and should be cached locally by date
  • Polar latitudes experiencing polar day or polar night return status codes indicating unoccurring rise or set events
  • Service availability is governed by US Navy web infrastructure maintenance policies

Access and pricing

Reference listing. Public feed access is separate from Fibric integration. If you request this feed, your quote covers the build, usage, and support.

Request USNO Astronomical Applications API ↗

Questions and answers

What is the difference between civil, nautical, and astronomical twilight?
Civil twilight occurs when the sun is between 0 and 6 degrees below the horizon and artificial lighting is generally not needed. Nautical twilight is 6 to 12 degrees below, and astronomical twilight is 12 to 18 degrees below.
Can the USNO API compute times for future or past years?
Yes. The underlying astronomical algorithms calculate celestial phenomena spanning hundreds of years past and future with high mathematical accuracy.
Is an API token needed to use the USNO web service?
No. The US Naval Observatory provides the API as an open public resource without API tokens or registration.
Ask about USNO Astronomical Applications API

Ask about the capabilities and requirements in this listing.

For project-specific requirements, contact Fibric.

This Commons signal listing is developed, published, and supported by Fibric. It reads public data published by US Naval Observatory (aa.usno.navy.mil). Upstream agencies and projects are the property of their respective owners, who are not affiliated with Fibric and do not sponsor or endorse this listing. Trademark policy