Rahu and Ketu are referred to in the sacred literature as the demons who consumed nectar and became immortal. In almost all books of astrology of India they are referred to but have rarely been praised. It may be because of their mystic nature and a lot of mysterious stories associated with both these planets.
Infact it is the greatness of our Vedic sages that they have been able to invent exact points or nodes of moon cutting the earth's orbit of sun. The point where the moon's north node cuts the earth's axis in the zodiac and thus makes a shadow on the zodiac is called Rahu and the South node of the moon is called Ketu. Ironically Rahu, the North Node which is looking towards earth signifies Materialism and Ketu which is in to the Darkness, as it is reversely pointed looks like tail Or symbolically an inward look in to the subconsciousness Or signifies Spirituality as Opposed to Rahu and both nodes are always 180 3/4 apart in the 360 3/4 12-House divided Zodiac.
According to some advanced techniques of modern predictions, a lot of research has been conducted on the Positive effects of Rahu and many eminent astrologers such as K.N. Rao, Dr. David Frawley and many astro research councils have come out with lots of interesting aspects and significance of Rahu and Ketu in one's horoscope. Rahu as such depending on its placement and strength etc. factors can some times give a tremendous and sudden mystical developments and great Raja Yoga karaka facilitator.
Rahu and Ketu play a significant role in giving interests Tantric and Mantra sadhanas and some times to the hight of extreme rebellious ritualistics. According to south Indian Dravidians, Rahu is nothing but Lord Shiva himself. Rahu is pleased when Ma Durga is worshipped.
Also there is another esoteric serpent symbolism associated with Rahu and Ketu to Kundalini Shakthi (Energy). The Head being Rahu (Signifying the different cosmic head petals of the Cosmic Snake Sahsrara Chakra or Awakening) and the tail being Ketu (Muladhara Chakra - Ganesha - or the beginning).
No one can ever master astrology but our finer techniques of astrological predictions cannot improve unless we discussed with open mind through presentation our predictions as case studies and more over, the effects and significance of mystery planets like Rahu and Ketu still offer a lot of scope in research, further study and application of principles of predictions.
A brief account of what is given about Rahu and Ketu in the sacred literature of India is being outlined here. It is useful to know it because the sacred literature of India contains not merely the account of planets and myths associated with them, but also gives us valuable clues which sharpen our astrological perceptions. The best researches in astrology can be done if we took seriously the stories about these planets, unravelled the mysteries, looked deeper into the stories, found richer astrological content than what is apparent and applied the principles so gleaned to horoscopes before us.
Nectar or amrita was churned out of the ocean (the story of Samudra Manthan). Poison too had come out with the nectar. That lethal poison could have destroyed the entire life on the life on the earth. Lord Shiva quaffed it off. He stored it in his neck as a result of which it became blue which is why one of the names of Lord Shiva is Lord Neelakantha.
It was decided to distribute the nectar to Gods and strengthen them against their fight with rakshas (demons). Without anyone noticing it at once, Rahu, and Ketu who were demons, joined the gods and partook of that nectar. When Lord Vishnu came to know of it further serving of nectar was not given to Rahu and Ketu. But they had enough consumed enough nectar to become immortal like gods. The Sun and the Moon had noticed this deceitful act of Rahu and Ketu and complained to Lord Vishnu. Lord Vishnu pierced the abdomen of Rahu and chopped off the head of Ketu. But they did not die as they had become immortal.
The Sun and the Moon had reported against Rahu and Ketu to Lord Vishnu. But they had become immortal now. They prayed to the almighty to include them in the galaxy of planets. Their wish was granted. But they harboured ill will towards the sun and the Moon who had reported against them.
Note: From this story the relation between the luminaries, Sun and Moon and Rahu and Ketu gives us rich material to work on for our research.
ANOTHER VERSION
The Skanda Purana story of Rahu is a repetition of the same with one difference. Gods and Demons had decided to churn the ocean to extract nectar. The emphasis is that demons were as much a part of the effort to churn the ocean as gods. When nectar was got, Lord Vishnu decided to give nectar only to gods, not to demons. Rahu came to know of this decision. He assumed the shape of a god and entered the group of gods to drink nectar. Lord Vishnu cut off the head of Rahu.
PRAYER TO RAHU
Some Oriental scholars both of India and of the west hardly know that the stotras or Sanskrit hymns, poems, stanzas or poetical compositions give valuable clues, mostly predictive astrological clues about the planets. Here is a very fine, celebrated poem on Rahu with approximate English transliteration and the meaning given below it:
Rahurdnava Mantri Cha Simhikachittanandah!
Ardhakayah Sada Krodhi Chandraditya Vimardanah! (1)
O! Giver of happiness to Simhika (his mother), minister of demons, half-bodied, Rahu is the tormentor of the Sun and the Moon.
Roudro Rudrapriyo Daityah Swarbhanurbhanur Bheetidah!
Graharajah Sudhapayi Rakatikshyabhilashuka! (2)
Terrible looking, devotee of Lord Shiva, king among planets, immortal because he has drunk nectar, Rahu who frightens the sun feels happy when he is worshipped at night.
Kaaldrishti Kaalroopa Shri Kantha Hridayaasrayah!
Vidhuntudah Saimhikayo Ghorarupo Mahabalah! (3)
His sight is death-inflicting: his looks are Death-like: he resides in the heart of Lord Neelakantha (Lord Shiva): has made the Moon lustreless. The son of Simhika is all powerful.
Grahapeedakaro Dranshtri Rakta netro Mahodarah!
Panchavimsati Namaani Smritava Rahum Sadanarah! (4)
He who torments planets, has big whiskers, has blood red eyes, beg bellied (hard to satisfy) these are the twenty five names of Rahu.
Yeh Pathet Mahati Peeda Tasya Nashyati Kevalam!
Arogyam Putramtulam Shriyam Dhanyam Pashumtatha! (5)
He, who recites these names, overcomes his troubles by a mere recitation of these names, gets sons, good health, prosperity, agricultural and cattle, wealth.
DadatiRahustasmai Yah Pathet Stotram Uttamam!
Satatam Pathet Yastu Jeevat Varsham Shatam Narah! (6)
He who recites this stotras constantly gets his wishes fulfilled and lives up to the age of one hundred years (long age). That is the fruit of reciting this hymn.
Note: Please note that it is very difficult to write Sanskrit (The Language of Gods) words in English script. Hence please consult good Devanagari Script books to pronunciate/practice to get exact phonetics chantings and mantra sound vibrations.."
Credit: practicing-wicca.blogspot.com