Old instruments
Marine Chronometer
Direct answer
Marine Chronometer is a precision timekeeper built to preserve reference time during a sea voyage.
Marine Chronometer is a shipboard reference clock used in historical astronomy, timekeeping, or navigation.
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At a glance
- Found in
- Historical Almanacs & Instruments
- Related
- Artificial Horizon, Chronometer, Astronomical Clock, Regulator Clock
Marine Chronometer is a shipboard reference clock used in historical astronomy, timekeeping, or navigation.
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The story behind Marine Chronometer
Marine chronometers became practical longitude tools after prolonged eighteenth-century development and sea trials.
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The Book of the Sky
How people learned to read the sky, from Babylon to the day you were born.
Why Marine Chronometer matters
Marine Chronometer matters because comparing local celestial time with reference-meridian time provides a route to longitude.
Marine Chronometer in practice: an example
Local noon compared with chronometer Greenwich time gives a longitude relationship of fifteen degrees per hour.
Where readings of Marine Chronometer go wrong
A common error is to treat an unchecked chronometer as exact or use one time source as the sole modern navigation safeguard.
Sources and editorial method
Research references used for this entry include:
- Royal Museums Greenwich: A Unique History of Timekeeping - Museum overview of marine chronometers, astronomical regulators, and the development of precision timekeeping.
- National Geospatial-Intelligence Agency: The American Practical Navigator - Official modern reference for navigation principles, celestial observations, sight reduction, and navigational tables.
- Source
- The Great Almanac Dictionary
- Category
- Historical Almanacs & Instruments
- Last updated
- 2026-09-26
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Common questions
What is a marine chronometer?
Marine Chronometer is a precision timekeeper built to preserve reference time during a sea voyage.
What do people get wrong about a marine chronometer?
A common error is to treat an unchecked chronometer as exact or use one time source as the sole modern navigation safeguard.
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