a solar eclipse (or lunar eclipse), then after one callippic cycle a New Moon (resp. Full Moon) will take place at the same node of the orbit of the Moon, and under these circumstances another eclipse can occur. References Further reading Jean Meeus, Mathematical Astronomy Morsels, Willmann-Bell, Inc., 1997 (Chapter 9, p. 51, Table 9A: Some eclipse periodicities) External links Online Callippic calendar converter as used in Ptolemy's Almagest Ancient Greek astronomy Calendars