mural quadrant

mural quadrant

(myoo -răl) See quadrant.

Mural Quadrant

 

an astronomical instrument used in the Middle Ages to measure the altitudes of celestial bodies. Mural quadrants were of large size, with a radius as great as 3 m. They were securely attached to the stone walls of observatories; generally the wall was in the plane of the meridian. The arc of the mural quadrant was divided into fractions of degrees and permitted the direction to a celestial body to be read to within tenths of a minute of arc. In the 16th century, Tycho Brahe made use of a mural quadrant in compiling his star catalog, which was one of the most accurate of that time. Mural quadrants went out of use at the end of the 17th century. They were replaced by meridian circles, which permitted the elimination of instrumental errors from observations and thus provided a considerable improvement in the accuracy of the observations. (SeeQUADRANT.)

References in periodicals archive ?
The shower's radiant is in the obsolete constellation Quadrans Muralis (the mural quadrant), off the handle of the Big Dipper between the head of Bootes and the arched back of Draco.
The Quadrantids derive their name from the constellation of Quadrans Muralis (mural quadrant), discovered by the French astronomer Jerome Lalande in 1795.
Two notable examples are: the 8ft mural quadrant made for the second Astronomer Royal Edmond Halley and the 12ft zenith sector device made for James Bradley, who succeeded Halley as Astronomer Royal in 1742.
The name is a bit of a mouthful and comes from a now obsolete star grouping identified and named Quad-rans Muralis (the Mural Quadrant) by Jerome Lalande in 1795.