In olden days, there were no sophisticated devices like the telescope to view the celestial object but still, ancient Indian seers were able to visualize planets, stars and other distant objects with their divya drishti(a higher form of intuitive power practiced through meditation, for more profound details check this blog post). With their wisdom, they did see the two cutting points of Earth’s and Moon’s elliptical orbit ie: the path of motion. They termed these cutting points as Rahu and Ketu, the former is north node and the later is the south node. For more details please watch this video. There are other mythological stories about Rahu and Ketu, I am not going into that.
How did they consider these nodal points have an impact on human lives?
The eclipse was an unsolved mystery for our ancestors, during early days humans were fascinated by the occurrence of eclipse and also the natural calamities associated with the timing of eclipse. Our ancient seers were observing the eclipse and they were studying the effect on eclipse on lives. Hence there were able to find these nodes. You may wonder how eclipse and Rahu/Ketu are related.
The relation between Eclipse and Rahu/Ketu
Solar eclipses occur at New Moon when the Moon is between Earth and the Sun. Similarly, the Lunar eclipses occur at Full Moon when Earth is between the Sun and the Moon. That said, the eclipse doesn’t occur every month. The Moon orbit is tilted few degrees in relation to the earth. So the Earth, Moon and Sun don’t always align. The Earth and Moon's orbit intersection(which is Rahu/Ketu) is the key for eclipse.
It is important to note that our seers found that when Moon’s longitude is within 9deg 38sec of Rahu/Ketu then lunar eclipse would occur. If this longitude becomes much closer then total lunar eclipse would happen else partial lunar eclipse would happen. When Moon’s longitude is greater than 12deg 18sec of Rahu/Ketu then lunar eclipse won’t occur(Source : From my book "Achieving success through astrological guidance")
Similarly, when the Moon’s longitude is within 15deg 21sec of that of Rahu/Ketu then solar eclipse would occur. If this longitude becomes much closer then total solar eclipse would happen else partial solar eclipse would happen. Similarly when Moon’s longitude is greater than 18deg 27sec of Rahu/Ketu then solar eclipse won’t occur. This is the method they still use to mark the day of an eclipse in traditional panchang.
The implication of Rahu/Ketu
There is a common notion that Rahu/Ketu is always bad which is far from the truth. Rahu and Ketu if well placed in the horoscope can give huge material success and spiritual inclination. I will explain that in the coming articles. I hope this article reveals the concept of Rahu and Ketu popularly used in Vedic astrology.