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Ephemeris Computation Office, NAOJ

The Ephemeris Computation Office, ECO, computes annual astronomical phenomena such as 24 Sekki including vernal and autumnal equinoxes; rising and setting of the Sun and the Moon; solar and lunar eclipses; planetary phenomena etc., and produces "Calendar and Ephemeris" each year. We announce its summary as "Reki Yoko" in the first official gazette issued in February. Since the information on koyomi or citizen's calendar is closely related to our human life, we also publish Chronological Scientific Tables ("Rika Nenpyo") and provide useful tools in our web site so that many people can utilize them at hand.

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