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Astronomical Table with Volvelle
A look at the timepiece called a volvelle. The volvelle was used to calculate the positions of the sun, moon, and stars of the Zodiac throughout the year. By turning the dial, which was made from layered parchment, one could mathematically determine the phases of the moon, the number of days in each month, and the sign that governs each hour of the day.

© J. Paul Getty Museum