positional astronomy

astronomy

Also known as: astrometry

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

July 1, 2026

Quick Summary

Positional astronomy is a branch of astronomy focused on precisely measuring the positions and movements of celestial bodies. This allows for applications like navigation and determining locations on Earth. Historically, astronomy was one of the first sciences to achieve sophisticated, predictive capabilities due to the stable and regular movements of celestial objects like the Sun, Moon, planets, and stars.12

Accurate measurements of stellar positions are crucial. They help determine a star's movement across the line of sight (proper motion) and along the line of sight (radial velocity) using techniques like spectroscopy and the Doppler effect. Modern surveying, while requiring greater accuracy than navigation, has largely moved away from celestial observations, relying instead on satellite-based global positioning systems that utilize the Doppler effect for precise location determination. Stellar positions are typically measured using the equatorial coordinate system, with right ascension and declination, and are referenced against distant galaxies to create a fixed frame of reference.345

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

5 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

star
Stellar positions
Accurate observations of stellar positions are essential to many problems of astronomy. Positions of the brighter stars can be measured very accurately in the equatorial system (the coordinates of which are called right ascension [α, or RA] and
Read More
Accurate observations of stellar positions are essential to many problems of astronomy. Positions of the brighter stars can be measured very accurately in the equatorial system (the coordinates of which are called right ascension [α, or RA] and
Read More

astronomical observatory
…to improve the accuracy of position measurements of celestial objects from a few minutes of arc (before the advent of the telescope) to less than a tenth of a second of arc.
Read More
…to improve the accuracy of position measurements of celestial objects from a few minutes of arc (before the advent of the telescope) to less than a tenth of a second of arc.
Read More

navigation
Direction finding
…steady winds blew) as on astronomical ones (the positions and apparent motions of the Sun and stars). The Mediterranean sailor could confidently distinguish the cold north wind from the warm south wind. Names were assigned to eight principal winds, and the directions of these winds became the eight equally spaced…
Read More
…steady winds blew) as on astronomical ones (the positions and apparent motions of the Sun and stars). The Mediterranean sailor could confidently distinguish the cold north wind from the warm south wind. Names were assigned to eight principal winds, and the directions of these winds became the eight equally spaced…
Read More