Quadrant (instrument)

A quadrant is a historical astronomical instrument with which the elevation angle and positions of celestial bodies have been identified.

Replica quadrant and modern kits are still in use, eg for amateur astronomers, for introductory measurement exercises and - in a developed form - for height determination in the forestry and construction.

The classic quadrant consists of a quarter circle with graduation, an associated readout device, a visor and a plumb bob. The measured star was sighted over iron sights. The position of hanging solder the quarter circle indicates the elevation angle.

Small quadrants were held in the hand, larger set on tripods. In these, the visor has been replaced by a measuring telescope from about 1650.

Davis Quadrant

Quadrant of Hevelius, 1644

Tycho's mural quadrant, 1600

Quadrant in the Copernicus Museum Frombork (Poland )

Mural quadrant

In addition to the portable quadrants large fixed appliances were built, the wall quadrant, so-called, with which a higher accuracy was achieved. So used the Danish astronomer Tycho Brahe in his observatory Uranienborg said after him Tycho's mural quadrant, with a quarter-circle of two meters radius. As to the late 17th century the equipment with standard telescope was to go to great mural quadrant as the main instrument of many observatories developed.