Lunar eclipse can be described as the situation in which Moon passes through some portion of the Earth's shadow. This happens when Sun, Earth, and Moon come in perfect or close alignment with each other, with Earth being in the middle of the celestial bodies. It is because of this that there is always a full moon on the night of a lunar eclipse. In other words, a lunar eclipse takes place only when there is full moon. The type and length of an eclipse depends upon the location of moon, relative to its orbital nodes.
Types of Lunar Eclipse
The shadow of Earth, which is the main cause of lunar eclipse, can be divided into two parts - umbra and penumbra. Umbra is the darkest part of a shadow, where there is no direct solar radiation. Penumbra, on the other hand, reflects the region where solar illumination is only partially blocked.
Penumbral Lunar Eclipse
In case of penumbral lunar eclipse, moon passes through Earth's penumbral shadow. In this case, there is not much noticeable darkening of the moon's surface. Since penumbral eclipses are very subtle, it is hard to observe them.
Partial Lunar Eclipse
In case of partial lunar eclipse, a portion of moon passes through Earth's umbral shadow. This is a pretty usual phenomenon and can be seen very easily, even with the unaided eye.
Total Lunar Eclipse
In case of total lunar eclipse, the entire moon passes through Earth's umbral shadow. When total lunar eclipse occurs, moon attains a vibrant red color and the totality can last up to nearly 107 minutes.
Danjon scale was devised by André Danjon, with the purpose of rating the overall darkness of lunar eclipses. It is denoted by L, which can range from 0 to 4.
It signifies very dark eclipse, in which the moon is almost invisible, especially at mid-totality.
It signifies dark eclipse, which is gray or brownish in coloration. In this case, one can distinguish the details, but only with difficulty.
It signifies deep red or rust-colored eclipse. It is characterized by very dark central shadow, with outer edge of umbra being relatively bright.
It signifies brick-red eclipse, in which the umbral shadow usually has a bright or yellow rim.
It signifies very bright copper-red or orange eclipse, where umbral shadow is bluish and has a very bright rim.