Understanding Eclipes

an eclipse (Greek verb: ekleipô, "to vanish", though it derives from the prefix 'ex-', "away from", and Greek 'leipein', "to leave") is an astronomical event that occurs when one celestial object moves into the shadow of another.

The term is most often used to describe either a solar eclipse, when the Moon's shadow crosses Earth's surface, or a lunar eclipse, when the Moon moves into the shadow of Earth. However, it can also refer to such events beyond the Earth-Moon system: for example, a planet moving into the shadow cast by one of its moons, a moon passing into the shadow cast by its parent planet, or a moon passing into the shadow of another moon. A solar eclipse is actually a misnomer; the phenomenon is actually an occultation


General phases of a solar eclipse

* The general eclipse begins when the Moon's penumbra cone starts to sweep across the Earth's surface.
* The total or annular eclipse begins when the Moon's umbra starts to sweep across the Earth's surface.
* The centrality begins when the axis of the Moon's shadow cone starts to sweep across the Earth's surface.
* The eclipse's maximum occurs when the axis of the Moon's shadow comes closest to the centre of the Earth.
* The centrality ends when the axis of the Moon's shadow finishes its sweep across the Earth's surface.
* The total or annular eclipse ends when the Moon's shadow finishes its sweep across the Earth's surface.
* The general eclipse ends when the Moon's penumbra finishes its sweep across the Earth's surface.


] Local phases of a solar eclipse

* First contact (also called first exterior contact) is the instant when the Moon's disc starts to cover the Sun's.
* Second contact (also called first interior contact) is the instant when the Moon's disc is entirely surrounded by the Sun's (for an annular eclipse) or the instant when the Sun's disc disappears completely behind the Moon's (for a total eclipse).
* Third contact (also called second interior contact) is the instant when the Moon's disc starts to come out of the Sun's (for an annular eclipse) or the instant when the Sun's disc reappears from behind the Moon's (for a total eclipse).
* Lastly, fourth contact (also called second exterior contact) is the instant when the Moon's disc clears the Sun's.

] Phases of a lunar eclipse


there are three types of lunar eclipses: penumbral, when the Moon crosses only the Earth's penumbra; partial, when the Moon crosses partially into the Earth's umbra; and total, when the Moon crosses entirely within the Earth's umbra.

The progression of a lunar eclipse

* First contact (also called first exterior contact) is the instant when the Moon starts to enter into the Earth's umbra.
* Second contact (also called first interior contact) is the instant when the Moon enters completely into the Earth's umbra. This is the beginning of totality.
* The maximum of the eclipse occurs when the angular distance between the centre of the Moon's disc and the centre of the shadow cone is at its smallest value.
* Third contact (also called second interior contact) is the instant when the Moon starts to come out of the Earth's umbra. This is the end of totality.
* Lastly, fourth contact (also called second exterior contact) is the instant when the Moon clears the Earth's umbra completely.