Brahe's mural quadrant — The quadrant (radius c. 194cm) was made from brass and was affixed to a wall that was oriented precisely north-south. The observer (right) views a star through the opposite opening (upper left) to determine the star's altitude as it passes through the meridian. An assistant (lower right) reads the time off a clock and another one (lower left) records the measurements. The area above the quadrant is filled with a mural painting showing several other of Brahe's instruments. See Brahe's description.
Photo Credit: Engraving from the book: Tycho Brahe (1598), Astronomiae instauratae mechanica, Wandsbeck. Downloaded from the online exhibition at the Royal Library; stitching by Axel Boldt, Public Domain, https://commons.wikimedia.org/w/index.php?curid=19389032