Earth-Moon System
An eclipse involving the Sun, Earth and Moon can occur only when they are nearly in a straight line, allowing one to be hidden behind another, viewed from the third. Because the orbital plane of the Moon is tilted with respect to the orbital plane of the Earth (the ecliptic), eclipses can occur only when the Moon is close to the intersection of these two planes (the nodes). The Sun, Earth and nodes are aligned twice a year (during an eclipse season), and eclipses can occur during a period of about two months around these times. There can be from four to seven eclipses in a calendar year, which repeat according to various eclipse cycles, such as a saros.
Between 1901 and 2100 there are the maximum of 7 eclipses in:
- 4 (penumbral) lunar and 3 solar eclipses: 1908, 2038.
- 4 solar and 3 lunar eclipses: 1917, 1973, 2094.
- 5 solar and 2 lunar eclipses: 1934.
Excluding penumbral lunar eclipses, there are a maximum of 7 eclipses in:
- 1591, 1656, 1787, 1805, 1917, 1935, 1982, and 2094.
Read more about this topic: Eclipse
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