Eclipses
A solar eclipse is total or partial darkening of the Sun seen from Earth by the passage of a satellite, such as the passage of the Moon between the Sun and Earth. A solar eclipse is only visible in a narrow strip of the surface of the Earth. When the Moon comes between the Sun and the Earth casts a shadow on a particular part of the land surface, and a given point on Earth can be immersed in the umbra or penumbra cone.
Those who are in the area in which projects the umbra will see the disk of the Moon to the Sun completely overlap, and in this case there will be a total solar eclipse. Those in an area intercepted by the cone of darkness, see the disk of the Moon only partially overlap that of the Sun, and has a partial solar eclipse.
There is also a third case, when the new moon is in the node to a greater distance from the mean, then its apparent diameter is smaller compared to normal and his album does not cover exactly the del Sol these circumstances, on a certain stretch of the Earth affects not the umbra but its extension, and has an annular solar eclipse, since some of the lunar disk glowing ring is visible.
As one of these situations occur in the eclipses, we talk about all areas of bias or annular, referring to this type of eclipse can be observed from any point on Earth’s surface. Because the motion of the Moon around the Earth and the Earth’s motion around itself, the shadow of the moon on Earth’s surface is moving at 15 km / s. The total phase for a given geographic point therefore does not exceed eight minutes. This area may have width and maximum length of 200 and 15,000 km respectively.
A lunar eclipse is the passage of a planetary satellite, the Moon, the shadow cast by the planet, so that direct illumination of the satellite by the sun stops. Occur only near the full moon phase, and can be viewed from wide areas of the earth’s surface, particularly around the hemisphere that is not illuminated by the sun, the moon is always above the horizon.
Normally the disappearance of the moon is not full, its disc is illuminated by light scattered by the atmosphere and becomes a red halo. The total shadow or umbra produced by the earth is surrounded by a region of partial shadow called the penumbra. In the early stages and the last lunar eclipse, the Moon enters penumbra.
Depending on whether or not the moon enters the umbra completely zone can be distinguished total eclipses of the moon, when the satellite is completely immersed in the umbra, the partial lunar eclipse, when it enters umbra only partly and only part of the lunar surface is visibly darkened, and the penumbral eclipses when the Moon passes only through the cone of shadow, hardly visible to the naked eye and visible only through proper photographic techniques.
The maximum total eclipses of the moon is 3, 5 hours. We define the magnitude of a lunar eclipse as the Moon’s path length through the umbra divided by the apparent diameter of the moon.
The study of lunar eclipses, as well as astronomical measurements to allow verification of the moments of contact between the disk of our natural satellite and the umbra, it is useful to examine indirectly the conditions of the atmosphere, as density and color of the umbra and penumbra cones are heavily influenced by the presence of ozone and dust suspended in the various strata of the atmosphere.
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