Old instruments
Precession Table
Direct answer
Precession Table is a table of corrections used to carry celestial coordinates between epochs as Earth's rotation axis slowly changes direction.
Precession Table is a coordinate-epoch conversion table used in historical astronomy, timekeeping, or navigation.
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At a glance
- Found in
- Historical Almanacs & Instruments
- Related
- Meridian Table, Transit Table, Declination Table, Right Ascension Table
Precession Table is a coordinate-epoch conversion table used in historical astronomy, timekeeping, or navigation.
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The story behind Precession Table
Precession tables allowed catalogue and navigation work to update coordinates long before software performed the transformation.
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Why Precession Table matters
Precession Table matters because catalogue positions must share an epoch before they can be compared or pointed accurately.
Precession Table in practice: an example
A nineteenth-century star position can be precessed toward a modern reference epoch before plotting.
Where readings of Precession Table go wrong
Precession does not include every source of motion; proper motion, nutation, aberration, and measurement error may also matter.
Sources and editorial method
Research references used for this entry include:
- U.S. Naval Observatory: Astronomical and Navigational Almanacs - Official descriptions of the Astronomical Almanac, Nautical Almanac, and their tabular data.
- Source
- The Great Almanac Dictionary
- Category
- Historical Almanacs & Instruments
- Last updated
- 2026-09-26
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Common questions
What is a precession table?
Precession Table is a table of corrections used to carry celestial coordinates between epochs as Earth's rotation axis slowly changes direction.
What do people get wrong about a precession table?
Precession does not include every source of motion; proper motion, nutation, aberration, and measurement error may also matter.
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