Old instruments
Equinoctial Ring Dial
Direct answer
Equinoctial Ring Dial is a folding ring instrument that indicates solar time on an equatorial hour scale when set for latitude and date.
Equinoctial Ring Dial is a portable universal sundial used in historical astronomy, timekeeping, or navigation.
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At a glance
- Found in
- Historical Almanacs & Instruments
- Related
- Hadley Quadrant, Mariner's Astrolabe, Gunter's Quadrant, Sector Instrument
Equinoctial Ring Dial is a portable universal sundial 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 Equinoctial Ring Dial
Ring dials joined portable timekeeping with the geometry of the celestial equator in early modern instrument making.
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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 Equinoctial Ring Dial matters
Equinoctial Ring Dial matters because its geometry makes equal-hour spacing visible and can work across many latitudes.
Equinoctial Ring Dial in practice: an example
A spot of sunlight passing through a date-set aperture can fall on the inner hour ring.
Where readings of Equinoctial Ring Dial go wrong
Equinoctial Ring Dial gives apparent solar time and depends on correct latitude, suspension, orientation, and safe use in bright Sun.
Sources and editorial method
Research references used for this entry include:
- 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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More in Historical Almanacs & Instruments
- Line of Position
- Meridian Circle
- Pelorus
- Repeating Circle
- Sun Sight
- Astronomical Table
- Computed Altitude
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Common questions
What is Equinoctial Ring Dial?
Equinoctial Ring Dial is a folding ring instrument that indicates solar time on an equatorial hour scale when set for latitude and date.
What do people get wrong about Equinoctial Ring Dial?
Equinoctial Ring Dial gives apparent solar time and depends on correct latitude, suspension, orientation, and safe use in bright Sun.
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