LUNAR ECLIPSES
Because the Moon's orbit lies more or less in the plane of the ecliptic, (the plane formed by the Earth and the Sun) the Moon regularly eclipses the Sun, and the Earth regularly eclipses the Moon. However, eclipses do not occur once a month because the Moon's orbit is inclined about 5o to the ecliptic plane. The ecliptic plane is called the "ecliptic" because it is the plane in which eclipses can occur. When the Moon is above or below the ecliptic an eclipse will not occur.
Solar eclipses
The Moon's shadow consists of a dark inner cone, the umbra, surrounded by an outer region of partial shadow called the penumbra.
The Moon's umbra and penumbra.
A solar eclipse occurs when the Moon comes between the Earth and the Sun, and the Earth, Sun, and Moon are all in the plane of the ecliptic. If the Moon only blocks out part of the Sun, it is a partial eclipse. If the Sun is completely covered, it is a total eclipse. However, the Moon's shadow is some 5000 kilometres less than the average Earth-Moon distance. This means that often the Moon fails to completely obscure the Sun, and a bright ring of light can be seen around the Moon's disc. This is an annular eclipse, and is more common than a total eclipse. During an annular eclipse, the Moon's penumbra reaches the Earth's surface, but the umbra does not.
During a partial eclipse the Moon fails to completely block the Sun.	An annular eclipse of the Sun occurs when only the penumbra reaches the Earth.	The Moon's umbra has to reach the Earth's surface to produce a total eclipse of the Sun.
During a total eclipse, the umbra reaches the Earth's surface. The umbra travels along the surface of the Earth at over 1800 kilometres per hour. For an observer during a total eclipse, the sky slowly darkens as the Moon moves across the Sun. The light becomes more like evening light than midday light. Once the Sun is completely eclipsed, the sky is as dark as night, temperatures have fallen, and birds and other animals behave as if it is night.
During a solar eclipse, the Sun's corona becomes visible, and additional optical effects become apparent - ripples of light on the ground. The Sun's light can also stream through lunar valleys on the Moon's limb, creating beads of light around the Moon. The Sun's prominences can often be seen on the Sun's limb.
The solar corona and prominences are visible during a total eclipse.
Lunar eclipses
A lunar eclipse occurs when the Moon passes into the Earth's shadow. The Earth, too, has an umbra and a penumbra. However, a penumbral eclipse of the Moon is hardly noticeable.
A lunar eclipse occurs when the Moon passes into the Earth's umbra.
During a total eclipse of the Moon, when the Moon is within the Earth's umbra, the Moon becomes very red. This is because sunlight is deflected by the Earth's atmosphere into the umbra. As the Earth's atmosphere scatters blue light, the light deflected into the umbra is reddened, and it is the reddened light that then illuminates the Moon.
The Earth's umbra contains reddened light deflected by the atmosphere.	The Moon is reddened during a lunar eclipse.	As the Moon enters and leaves the umbra the Moon becomes white (grey) and red.