Old instruments
Cross Staff
Direct answer
Cross Staff is a graduated staff with sliding vanes used to measure the angular separation of two directions.
Cross Staff is a historical angular-measurement staff used in historical astronomy, timekeeping, or navigation.
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At a glance
- Found in
- Historical Almanacs & Instruments
- Related
- Declination Table, Right Ascension Table, Backstaff, Davis Quadrant
Cross Staff is a historical angular-measurement staff used in historical astronomy, timekeeping, or navigation.
An engraved functional orientation; the page explains the real instrument, method, or publication.
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The story behind Cross Staff
Cross-staffs served astronomy, surveying, and early navigation before backstaffs and reflecting instruments reduced difficult sighting.
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The Book of the Sky
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Why Cross Staff matters
Cross Staff matters because it translated similar-triangle geometry into a portable observation of altitude or separation.
Cross Staff in practice: an example
A navigator could align one vane edge with the horizon and the other with a star to estimate altitude.
Sources and editorial method
Research references used for this entry include:
- Royal Museums Greenwich: Cross-staff Collection - Collection records for cross-staffs and their vanes as historical angular-measurement instruments.
- Royal Museums Greenwich: Astronomical and Navigational Instruments - Museum reference collection for historical observing, calculating, timekeeping, and navigation instruments.
- Source
- The Great Almanac Dictionary
- Category
- Historical Almanacs & Instruments
- Last updated
- 2026-09-26
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Common questions
What is Cross Staff?
Cross Staff is a graduated staff with sliding vanes used to measure the angular separation of two directions.
Why does Cross Staff matter?
Cross Staff matters because it translated similar-triangle geometry into a portable observation of altitude or separation.
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