HM Nautical Almanac Office (HMNAO) (HMNAO)

The UK office that produces and supplies authoritative astronomical data for navigation, astronomy and timekeeping.

HMNAO is part of the UK Hydrographic Office and calculates ephemerides and related data used in publications including the Nautical Almanac, produced jointly with the United States Naval Observatory.

Its data supports celestial navigation and other applications, but users must apply the correct publication edition, time scale, interpolation and sight-reduction method.