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Lunar Eclipe Story
For a lunar eclipse to occur, the Earth must be located in a line, directly between the Sun and Moon, a configuration called
syzygy. Only then can the Moon move completely into the
umbra portions of the Earth′s shadow.
The type of lunar eclipse and length of time inside the umbra shadow depends on the proximity of the moon to either one of the two
orbital nodes at which time the moon is on or very near to the
ecliptic plane.
Too, a lunar eclipse can happen only when the Moon is full, and repeat occurrences of these lunar phases from
full moon to
full moon result from solar and lunar orbits producing the Moon′s synodic period of 29.53059 days.
Lunar Saros Series
Each and every lunar eclipse is a part of a family of eclipses, with all the members of that family sharing a very similar geometry. This family of eclipses, known as a Lunar Saros Series, contains from 69 to 87 individual eclipse events with each of the individual family members separated by one
saros cycle.
Every lunar saros series is given a specific saros series number and each lunar saros series lasts between 1200 and 1600 years. All of the lunar saros series with even numbers exist at the ascending node of the moon′s orbit, while all of the lunar saros series with odd numbers occur at the descending nodes.
Lunar Saros Series have been indexed as -20 to zero and from 1 to 183 which have been active since about 3200 BCE and will continue until 4000 CE.
Lunar eclipses are somewhat rare events, but not as rare as solar eclipses, because unlike solar eclipses which can only be viewed in a specific geographical area, lunar eclipses can be viewed from anywhere on the dark side of the Earth.
Precise Alignment
As explained above, a total lunar eclipse can only occur when the Moon passes directly behind the Earth into the umbra. Also, this can only occur when the sun, Earth, and moon are aligned in a straight line and only during a full moon.
However, due to the fact that the orbit of the Moon is inclined at 5.14° from the ecliptic plane, during most full Moons, the shadow of the Earth misses the Moon entirely and instead is cast into space above or below the Moon.
Thus, a total lunar eclipse can only occur with the exact alignment of the Sun, Earth, and Moon at which time the moon is in or very near to one of its two
nodes which will ensure that the moon is fully enveloped within the umbra.
The Saros Cycle
After a period of one saros cycle after an eclipse, the Sun, Earth and Moon return to a straight line in the same relative geometry and at that time, a nearly identical eclipse will occur.
Thus, a saros cycle is a period of time used for predicting when an eclipse will occur and has a length of 6585.3211 days. Also, a saros cycle does not just predict any eclipse, instead, it identifies intervals between eclipses that are in the same saros series or family. This family of eclipses are all nearly identical in geometry, occur at the same lunar orbital node at nearly the same distance from Earth and at nearly the same time of the year.
The saros cycle length may consist of either:
14 common years plus 4 leap years and 11 days and 8 hours, or
13 common years plus 5 leap years plus 10 days and 8 hours.
However, due to the fact that one saros cycle is a period not equal to a whole number of days, this causes subsequent eclipses of the same saros series to be visible from different parts of the Earth
Into The Umbra
This Gallery will highlight some of the total eclipses photographed while the moon has journey into the earth′s umbra.
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