An instrument used before the invention of the telescope to measure the angle above the horizon of astronomical objects as they crossed the meridian. It consisted of a large arc engraved with an angular scale, mounted vertically on a north–south wall. If the arc covered 90 ° (a quarter-circle) it was known as a mural quadrant. A sighting device allowed the altitude above the horizon of a chosen star to be measured.
Subjects: Astronomy and Astrophysics.