A Short Guide to Celestial Navigation [pdf]
This PDF guide provides an introduction to celestial navigation, covering key concepts such as the celestial sphere, coordinates, and the use of a sextant to determine position at sea using the Sun, Moon, stars, and planets.
Background
- This is a practical guide to celestial navigation — finding your position on Earth by measuring the sun, moon, stars, and planets with a sextant. It was written before GPS made the technique mostly obsolete for everyday use.
- The methods described (using a sextant to measure altitudes of celestial bodies, then reducing those sights with almanac data and sight reduction tables to get a position line) were standard practice for ocean navigators from the 18th century through the late 20th century.
- Key concepts: the sextant (an optical instrument that measures the angle between a celestial body and the horizon), the Nautical Almanac (a yearly publication with predicted positions of sun, moon, planets, and stars), and sight reduction tables (mathematical tables that turn altitude measurements into a line of position on a chart).
- Celestial navigation remains taught as a backup to GPS and a core skill for offshore sailors, and is still used by some military and recreational navigators who want a fully independent position-fixing method.