The Two-Metre Brass Arc That Made Tycho's Pre-Telescopic Astronomy Possible
The mural quadrant at Tycho Brahe's Uraniborg observatory was a brass arc mounted on a north-south wall and used for measuring the meridian altitudes of stars and planets. It was the largest and most accurate astronomical instrument of the pre-telescopic period and produced most of the data that Kepler would later use to derive the laws of planetary motion.
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