Nautical almanac

The Almanac specifies for each whole hour of the year the position on the Earth's surface (in declination and Greenwich hour angle) at which the Sun, Moon, planets, and First Point of Aries[clarification needed] is directly overhead.

[1] [2] In the United States, a nautical almanac has been published annually by the US Naval Observatory since 1852.

A good example would be Brown's, which commenced in 1877, and is still produced annually, its early 20th-century subtitle being "Harbour and Dock Guide and Advertiser and Daily Tide Tables".

[5] The "Air Almanac" of the United States and Great Britain tabulates celestial coordinates for 10-minute intervals for use in aerial navigation.

To find the position of a ship or aircraft by celestial navigation, the navigator measures with a sextant the apparent height of a celestial body above the horizon, and notes the time from a marine chronometer.