Mariners / Gunter's Quadrant


This is a wooden replica of a late 17th / early 18th century quadrant featuring a Gunter's Quadrant on one side and a simplified Mariners Quadrant on the reverse side.

The Gunter's quadrant is a simplified version of the elegant, but complicated, Arabic astrolabe. It is typically a brass or wood instrument with a scale of 0 to 90 degrees. It has two peepholes along one edge for sighting the sun, the moon, stars or the planets. The astrological figures on the quadrant were typically calculated for a specific latitude which limits the instrument's usefulness at sea. A plum bob on a string falls across the scale to indicate the altitude, or angle of elevation, of the celestial body above the horizon. The brass is engraved with several geometrical figures: a scale for the declination of the sun above or below the equator, a stereo-graphic projection of the equator, the signs of the Zodiac, and the positions of several stars around the north pole. A shadow square for solving plane triangles was provided.

The instrument is named for Edmund Gunter, an outstanding mathematician specializing in spherical trigonometry as it applied to astronomy, who was born in Hertfordshire England in 1581. He first described the quadrant in the 1623 publication "De Sectore & Radio." While Gunter never manufactured the quadrant it was produced by professional instrument makers.

The principle use of the quadrant was to tell the time of day. After the observer used the quadrant to determine the altitude of the sun; determined the declination of the sun for that date; and determined his latitude the scales could be used to determine the time.

Our Quadrant is approx. 9.5" high by 9.5" wide and is made from 3/4" thick Oak treated with linseed oil