Dictionary term
Davis Quadrant
Direct answer
Davis Quadrant is a backstaff with graduated arcs and vanes designed chiefly for measuring the Sun's altitude at sea.
Davis Quadrant is an arc-form backstaff used in historical astronomy, timekeeping, or navigation.
Davis Quadrant is an arc-form backstaff used in historical astronomy, timekeeping, or navigation.
An engraved functional orientation; the page explains the real instrument, method, or publication.Quick reference
- Use when
- Use Davis Quadrant by setting the shadow vane on one arc and making the fine horizon alignment on the other.
- Do not use it for
- A rolling horizon, worn scale, misplaced vane, or poor shadow edge can make the reading unreliable.
- Reference category
- Historical Almanacs & Instruments
- Related terms
- Cross Staff, Backstaff, Octant, Reflecting Circle
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The story behind Davis Quadrant
Named for John Davis, the design was refined by later makers and used widely in seventeenth- and eighteenth-century navigation.
Davis Quadrant in spiritual tradition
Davis Quadrant rewards careful observation, explicit assumptions, and humility about the limits of every model or measurement.
Davis Quadrant: fact and faith, kept distinct
This is a factual history-of-science, instrument, timekeeping, or navigation reference. It may support wonder and disciplined attention without becoming a claim of fate, worship, or private revelation.
Davis Quadrant in numerology
Davis Quadrant is not a numerology claim. Any numbers attached to it should retain their ordinary scientific, calendrical, navigational, or historical meaning unless a separate symbolic interpretation is clearly labeled.
Why Davis Quadrant matters
Davis Quadrant matters because its two-arc layout improved range and scale reading while preserving shadow-based observation.
Davis Quadrant at work: an example
A mariner could observe meridian altitude without looking along a line aimed at the Sun.
Where interpretation stops
Davis Quadrant is presented as sourced astronomy, calendrical, Earth-science, cultural, or instrument-history reference. Definitions should distinguish measured phenomena from civil convention and historical interpretation, preserve location and time dependencies, and avoid turning factual sky data into a deterministic personal claim.
Sources and editorial method
Research references used for this entry include:
- Royal Museums Greenwich: Backstaff - Museum documentation of the backstaff, its arcs, vanes, scales, and solar-altitude use.
- 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
- Also appears in
- Historical Almanacs & Instruments
- Aliases
- None listed
- Last updated
- 2026-07-16
Explore Davis Quadrant
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More in Historical Almanacs & Instruments
- Greenwich Hour Angle
- Longitude by Chronometer
- Mural Quadrant
- Planet Sight
- Sector Instrument
- Transit Instrument
- Artificial Horizon
- Canon of Eclipses
Common questions
What is Davis Quadrant?
Davis Quadrant is a backstaff with graduated arcs and vanes designed chiefly for measuring the Sun's altitude at sea.
How is Davis Quadrant used in an almanac?
Use Davis Quadrant by setting the shadow vane on one arc and making the fine horizon alignment on the other.
What should I avoid when interpreting Davis Quadrant?
A rolling horizon, worn scale, misplaced vane, or poor shadow edge can make the reading unreliable.
