Nautical Almanac

An annual publication of predicted astronomical data used for celestial navigation and related calculations.

It tabulates the Greenwich Hour Angle and declination of the Sun, Moon, navigational planets and selected stars, together with auxiliary information for reducing observations and determining time. National almanacs may also contain sunrise, sunset, twilight and other reference tables.

A nautical almanac is date-specific and is not a general substitute for charts, sailing directions, tide tables or notices to mariners. Printed or electronic data must cover the observation date and use the intended time standard and interpolation method.