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Equation Clock
1591
Jost Bürgi
This marvel is the first clock in history with a moon mechanism based on Nicolaus Copernicus's theory of the lunar orbit. It is also the only timepiece in the history of astronomy whose pictorial program reflects its astronomical readings and places those activities at a particular court. An astute patron could read the difference, or "equation," between the true and mean movements of the sun and moon from the clock's hands. The court clockmaker made it for Landgrave William IV of Hesse-Kassel, a learned patron who was considered to be among the most accomplished astronomers of the sixteenth century. |