Solar and lunar eclipses are possible when the Sun, Moon and Earth are on the same line. Astronomers say that the Moon is in the node of its orbit, and the position of the Sun in the sky must. A solar Eclipse happens when the Moon is between the Sun and Earth, i.e. new moon.

However, to the shadow of the moon fell to the Earth, must run a number of conditions. They arise due to the fact that the diameter of the moon less than the sun about 400 times, but the distance from the Earth to the moon 400 times smaller: 384 000 km 149 500 000 km, respectively. So the full shadow of the moon is a very narrow cone, facing the top to the Ground.


Where this cone will pass through the earth's surface, there is a total solar Eclipse. It will be seen in a strip about 300 km. It depends on the current distance to the moon, which is slightly changing, as the moon's orbit is elliptical, somewhat elongated.

The penumbra of the moon forms, on the contrary, the expanding cone. On the Ground he will take the tape width of 3000-6000 km, framing strip full shade. It will be a partial solar Eclipse. It is possible that Umbra does not reach Earth. Then we will see an annular Eclipse.

The periodicity of eclipses



If the orbit of the Earth and the moon were exactly circular and has not hesitated in the transverse plane, the Eclipse of the Sun still might not happen every lunar month is 29.5 days. Due to the rotation of the Earth around the Sun, the nodes of the lunar orbit slowly shifted towards the visible movement of the Sun, making a complete revolution in the Ecliptic over 6585 days and 8 hours, or 18 years 11 days 8 hours.

Scientists in ancient times called the period of "repetition" – the Saros. If you know that somewhere on Earth at some day there was an Eclipse, it will be repeated after a Saros. If within one Saros was observed several eclipses, they are visible through the Saros, but in other places. And knowledge of the Saros, it is able to determine exactly when the Eclipse will happen in the same place: for "balance" in 8 hours the Earth will rotate a third of a turn. Impact and other factors.

The shift of the apogee and the precession



The fact, first, that the long axis of the lunar orbit due to the influence of other planets slowly turns toward a visible movement of the Sun. Astronomers call this phenomenon the shift of the peak. As a result of it, the Sun is at the nodes of the moon's orbit every six months (182,5 days), and every 174 days. It already knocks "perfect" rhythm of the eclipses.

Second, the moon's orbit is also subject to precession. She would slowly sways. Because of the precession of the lunar shadow cone can pass by the Earth, as shown in the inset in the figure. Then the penumbra will fall on high latitudes – the Arctic or the Antarctic.

When waiting for Eclipse?



Because of all the factors mentioned above the whole Earth in the year may not be less than 2 and not more than 5 years of eclipses. Five happens if the first was at the beginning of January. Then the following will happen in February, then – in the middle of summer, and another two in November and December. But they will be visible in different places.

In the same place the solar Eclipse occurs on average once every 274 years, i.e., once every 250-300 years. But is an average worldwide value, strict periodicity is not here. In Moscow, a total Eclipse was observed:

· On 11 August 1124.
· March 20, 1140.
· June 7, 1415.
· 26 APR 1827 – shaped.
· August 19, 1887.
· July 9, 1945, almost full, its phase was 0.96, that is, the Moon covered 96% of the visible surface of the Sun.

February 15, 1961, observed a partial Eclipse. 16 Oct 2126 year in Moscow will happen next total solar Eclipse. Before him, Russia will be seen more 4 of a total Eclipse, only in the far North of Siberia and in the Arctic.

For the current, 2014, the calculation gives two eclipses: April 19 – annular in the southern hemisphere, in Australia, then in Indonesia. October 23 will be a partial Eclipse. It can be observed in Kolyma, Chukotka, then in Canada and the United States.

The duration of eclipses



A total solar Eclipse lasts between 3-7 minutes depending on the astronomical circumstances. Partial may last an hour and a half.

It is possible to calculate the Eclipse yourself?



Unfortunately, no, especially if we are talking about this particular item. Consideration of all factors contributing to Eclipse more and more. To make something like a calendar of eclipses for each city astronomers is not taken now. However, information about future eclipses they have. In Russia the Eclipse calculated at the Pulkovo Observatory. According to him, after sitting over the map, you can make a calendar of eclipses for themselves.