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A large frame quadrant at the Beijing Ancient Observatory. It was constructed in 1673.
A quadrant is an instrument used to measure angles up to 90°. Different versions of this instrument could be used to calculate various readings, such as longitude, latitude, and time of day. It was first proposed by Ptolemy as a better kind of astrolabe. Several different variations of the instrument were later produced by medieval Muslim astronomers. Mural quadrants were important astronomical instruments in 18th-century European observatories, establishing a use for positional astronomy.
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Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).