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Gunter Quadrant

Edmund Gunter, an English mathematician, described this type of pocket-sized instrument in 1618. Like other horary quadrants, this one is designed to find the time of day by finding the altitude of the sun. When the sunlight passes through the two sights on the top edge of the instrument, a thread with a weight on the end indicates the altitude. The Gunter quadrant is unique in that it is also imprinted with projections of the tropics, equator, ecliptic and the horizon. Using these scales and curves along with related tables, a mariner or surveyor could sight the sun, moon, or stars to find the time of day or night, the date, the length of the day, the times of sunset and sunrise, and the meridian. The Gunter quadrant was cheap, portable, and compact, but because its scales and lines applied to only one specific latitude, it was primarily used on land.

Ref: Bennett, J.A. The Divided Circle: A History of Instruments for Astronomy Navigation and Surveying (Oxford: Phaidon, 1987), p. 79-80.

Waters, David W. The Art of Navigation in England in Elizabethan and Early Stuart Times (New Haven: Yale University Press, 1958), p. 438.

Gunter, Edmund, The Works of Edmund Gunter…(London: F. Eglesfield, 1673), p. 113-120.


Gunter Quadrant
Gunter Quadrant (TD)