Saros cycle
About the Saros cycle
Eclipses recur after 223 synodic months, about 18 years and 11 days, because the Sun, Moon and lunar nodes return to nearly the same geometry. Babylonian scribes predicted eclipses from it, and Edmond Halley borrowed the name saros from Babylonian lists. The cycle shifts each return about 120 degrees west in longitude and 5 degrees north in latitude, so a watcher sees a similar eclipse every 54 years.
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