Saros

Astronomers discovered that eclipses occur at regular intervals. The same eclipse is repeated every 18 years and 10 days (or 11 if it is a leap year). This period is called a saros. Thanks to the saros, the exact date of an eclipse that occurred several centuries ago can be ascertained. Similarly the next eclipses can be predicted.

The 11 August 1999 eclipse will therefore be exactly repeated under the same conditions and duration on 21 August 2017. But because of the rotation of the Earth on its axis, it will not occur at the same place and at the same time of day on Earth. There are approximately 84 eclipses in a saros. 42 lunar and 42 solar. There are between four and seven eclipses per year, with at least two lunar and two solar; Most of them are partial eclipses. An eclipse only occurs at the same place approximately once every 370 years. The distance from the Moon to the Earth increases by ½ cm per year. Thus in several hundred centuries, total eclipses will no longer occur.