Phases of Moon
Moon is one of the important planets of planetary kingdom. Moon has great power of attraction and it is this attraction of Moon that certain scientific phenomena take place like neap tide and spring tide, eclipse, seismic events etc.
Moon has the tendency to wan or wax for a continuous period of 15 days. The changing position of Moon every night is termed as the phases of Moon. In this chapter we will study how these different phases of Moon affect the nativity.
Features of Moon
There are three important features of Moon:
- Moon is non-luminous satellite
- It revolves around the earth
- Its orbit is 5° inclined from the ecliptic
Phases of Moon
If we suppose that the Sun rays fall vertically over Moon then the part which receive Sun rays will be illuminated. The part where Sun rays do not fall will remain dark as it is shown. Now if we see Moon standing on the earth, then we will see Moon as complete blank.
On Purnima, Moon appears fully illuminated shown as no. 1 in the figure. On Amavasya day Moon will appear no. 5 in the figure. That's why, the travel of Moon has been shown as Krishna paksha when the phase of Moon decreases gradually and as shukla paksha when the phase of the Moon increases gradually.
Sun is a star and only luminary celestial body in the solar system. Other planets reflect the Sun rays coming to them. Each planet has its own gravitational force and due to its effects they attract and repel one another.
Lunar eclipse takes place when Moon comes across the shadowy area while travelling on its path, see the figure
It happens only when Sun, Earth and Moon comes in a straight line. Orbit of Moon forms 5° angle on ecliptic. So, whenever these 3 planets come in a straight line, then Moon may or may not be near the bottom surface of ecliptic. So Moon either may or may not be in a straight line. Whenever, Moon happens to be in the straight line with Earth and Sun on Purnima day then lunar eclipse takes place.
Lunar eclipse takes place only when Sun, Earth and Moon are in a straight line on Purnima day and Moon is exactly near Rahu or Ketu point. When the whole disc of Moon come across the shadow of earth then total lunar eclipse takes place. When some part of the disc come across the shadow then partial lunar eclipse takes place.
In the above figure Sun, Earth and Moon are shown in a straight line on Purnima day. Cone A, B, D has been shown black because this area is not receiving any Sunlight. Cone A, D, R and B, S, D have been shown in light black shade because these areas are receiving partial Sunlight.
Whenever Moon passes through the full shadow area then total lunar eclipse takes place. Total duration of Lunar eclipse is never more than 1 hour 45 minutes. During this entire duration Moon remains passing through the deep shadow area.
Solar Eclipse takes place when Moon comes between Sun and Earth in a straight line. This happens on Amavasya (New Moon) when Moon is near Rahu or Ketu point.
The causes of solar eclipse are also the same like that of lunar eclipse. In solar eclipse only Moon is situated between Sun and Earth.
During total solar eclipse the entire disc of Sun is not visible. In partial Solar eclipse, some part of Sun's disc is visible. There is another type of solar eclipse which is called Angular Solar Eclipse. This solar eclipse takes place when Moon is at the farthest distance from earth and Sun is at the nearest distance to the earth.
Other conditions are the same. Angular solar eclipse takes place because the virtual angular diameter of Moon is less than the angular diameter of Sun. Due to this Moon is not able to cover Sun in entirety. Moon only covers the centre of Sun and due to this Sun appears as a diamond ring.
How to determine Eclipse in a horoscope
As discussed earlier, it is essential either for Sun or Moon to come in close proximity to the nodes i.e. Rahu or Ketu for the occurrence of eclipse. If Sun comes in close proximity to Rahu or Ketu then solar eclipse may occur and when Moon touches the longitude of Rahu or Ketu then lunar eclipse takes place.
Sun generally touches the nodes twice a year or maximum three times and Moon comes in proximity to the nodes minimum twice every month. But, eclipse does not take place every time Sun or Moon touches the nodes.
For the occurrence of eclipse, both Sun & Moon need to touch the nodes. At this time Sun, Moon & Earth automatically comes in a straight line.
In the horoscope, whenever Sun conjuncts Rahu or Ketu and Moon is in opposition irrespective of house or sign, it is a condition of lunar eclipse as shown above:
Similarly if Sun conjuncts with Moon along with Rahu or Ketu Solar eclipse takes place. If Sun conjuncts Rahu or Ketu, it forms Grahan yoga because Lunar or Solar eclipse has occurred recently or will occur in near future.
This is because of the fast movement of Moon which moves from conjunction to opposition in just 15 days Moon's conjunction's with Rahu or Ketu is not a grahan yoga because it may take few months when Sun may conjunct Rahu or Ketu again.
If Sun and Moon both are in conjunction with Rahu or Ketu then it is a condition of full grahan yoga.
Some noteworthy facts about eclipse
There may be maximum 7 eclipses in a year.
There are minimum 2 solar eclipses in a year.
- The cycle of eclipses repeat itself after 18 years 11 days. This is called Saros Cycle.
- Lunar eclipse occurs more than solar eclipse.
- Lunar eclipse must take place before or after solar eclipse.
- Lunar eclipse may occur only when Sun is about to touch Rahu or Ketu within 9 days.
- Maximum distance between Sun and Rahu/Ketu can be 18.5° for solar eclipse.
For lunar eclipse, the distance between Sun and Rahu/Ketu should essentially be less than 12.1°. For total lunar eclipse, it should be less than 5°.
- The maximum period of lunar eclipse can be 1h 45m.
- The maximum duration of total solar eclipse is 7m 30s.