The ''plinthis'' (block) of Hipparchus

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The ''plinthis'' (block) of Hipparchus


It was a simple astronomical instrument suitable to calculate the latitude of a place. It consisted of a graduated quadrant, which was engraved on a square block oriented towards the South. Two pegs were placed at the top and bottom of the quadrant to determine the verticality with the help of a plumb. The upper peg was also used as a gnomon. The latitude of the area was equal to the indication of the gnomon's shadow during the spring or autumn equinox, or the average indications of the gnomon's shadow during the summer and winter solstice.

SOURCES: "Ptolemy, The Great Syntaxis of Astronomy (Almagest)"