The mural quadrant was a type of astronomical instrument used to measure the altitude of celestial objects. It was primarily used in the 17th and 18th centuries by astronomers to catalog star positions and track the movement of planets.

Here are some famous astronomers who utilized mural quadrants:

* Tycho Brahe (1546-1601) was a Danish astronomer who extensively used a mural quadrant to make precise observations of the stars and planets. He made over 777 stars in his catalog.

* Giovanni Domenico Cassini (1625-1712) was an Italian astronomer who also used a mural quadrant to study planets and moons. He discovered four moons of Saturn.

* James Bradley (1693-1762) was an English astronomer who used a mural quadrant to discover the aberration of starlight, a phenomenon that explained the apparent shift in the position of stars due to the Earth's motion.

It's important to note that the mural quadrant was later replaced by more accurate instruments like the transit telescope and meridian circle, which enabled even more precise measurements.