Approximately every 30 days the Moon turns its unilluminated face towards the Earth at New Moon. An observer looking down on the north pole of the ecliptic would then see the Sun, Moon and Earth in a straight line. Despite this, the shadow cast by the Moon rarely touches the Earth. Because of the inclination of its orbit, at the time of New Moon the Moon is usually above or below the Earth’s orbital plane, so its shadow misses the Earth. The Moon crosses the ecliptic on only two days each month, but if one of these dates coincides with New Moon, then the Sun, Moon and Earth are in line, and the Moon’s shadow falls on part of the Earth. Overall, such a solar eclipse occurs twice a year. Anyone within the umbra, which is about 100 km across, sees a total eclipse of the Sun. This is a relatively small area, so few persons ever have the opportunity of witnessing a solar eclipse.
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- T. Oppolzer; Canon der Finsternisse Denkschriften der Math.-Naturw. Classe der Kaiserlichen Akademie der Wissenschaften Bd. 52, Wien (1883); Dover Publications, Inc., New York (1962). Elements for solar and lunar eclipses for the period -1207 to 2163. Maps of the paths of the centre line for total solar eclipses.Google Scholar
- H. Mucke, J. Meeus; Canon of Solar Eclipses, -2003 to 2526 Astronomisches Büro, Hasenwartgasse 32, Wien (1984). Elements for 10774 solar eclipses for about 4500 years on the basis of Newcomb’s theory of the solar orbit, and Brown’s lunar theory. Simple diagrammatic charts showing the approximate path of the centre line. The book Astronomical Algorithms by J. Meeus  describes various methods, which are particularly suitable for rapid prediction and assessment of possible eclipse dates. Ready to use tables for all kind of solar eclipses are given in . The classical method of calculating solar eclipses using Besselian elements is described in the Explanatory Supplement  and in Mueller .Google Scholar