U.S. Naval Observatory
- Astronomical Applications Department
- USNO Circular 179
- USNO Julian/Calendar date conversion
- Additional USNO data services
H.M. Nautical Almanac Office
International Astronomical Organizations
- IAU: International Astronomical Union
- IERS: International Earth Rotation and Reference Systems Service
- SOFA: IAU Standards of Fundamental Astronomy
- CDS: Centre de Données astronomiques de Strasbourg
Products provided by International Astronomical Organizations
- IERS Earth Orientation data
- IERS Bulletins A, B, C and D description
- IERS Technical Notes
- IAU 2006 series for CIP & CIO
- IAU 2000A nutation series for Δψ and Δε,
- lunisolar nutations at ftp://tai.bipm.org/iers/conv2003/chapter5/tab5.3a.txt
- planetary nutations at ftp://tai.bipm.org/iers/conv2003/chapter5/tab5.3b.txt