Book excerpt: The Almanac provides key astronomical information for every kind of sea-going vessel, from cruise liners to fishing boats. It contains tabulations for the Sun, Moon, planets and stars, for use in the determination of position at sea from sextant observations. It also gives details of: times of sunrise, sunset, twilights, moonrise and moonset for use in the planning of observations; interpolation and altitude correction tables; the phases of the Moon; a pole-star table; diagrams and notes for the identification of stars and planets; information on eclipses of the Sun and Moon; and the standard times of most countries. It is prepared jointly by H.M. Nautical Almanac Office and the US Naval Observatory, to meet the requirements of the Royal Navy and the US Navy.