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In short
Rahu is the Moon's ascending node, counted as the eighth of the nine grahas in BPHS although it is a point, not a body. This app computes it as the mean node, places Ketu exactly opposite, marks both retrograde, and treats Rahu as a natural malefic with an 18-year Vimshottari period.
What the term means
Rahu is the point where the Moon's path crosses the Sun's path going north - the ascending one of the two lunar nodes. It has no body, but Jyotish counts it as a graha with a sign, house and nakshatra like any other. In this app Rahu is the mean node, and Ketu is always the point exactly 180 degrees from it.
Where the term comes from
BPHS Ch. 3 Sl. 10 lists Rahu eighth among the nine grahas, and Sl. 11 puts Rahu and Ketu among the malefics, the translation adding that they are the ascending and descending nodes of the Moon. Sl. 14-15 say the two "form the Grah Army". Saravali Ch. 4 Sl. 1-2 makes Rahu the ego of the Kalapurusha. On signs, BPHS Ch. 47 Sl. 34-39½ gives Rahu exaltation in Vrishabh, Mooltrikon in Mithun and own sign in Kumbh, and records that some sages give Kanya instead. The Bhrigu Sutras call the nodes "shadowy planets" and say they own no signs (Part I, pp. 4 and 12-13), noting that the ancients disagree on their signs.
How this app uses it
- Position: computeChart() takes meanLunarNode() for the birth moment, subtracts the Lahiri ayanamsa, and sets Rahu's retrograde flag to true by convention. The true node is computed only as a check inside the Kaal Sarp calculator.
- Nature: Rahu is in the MALEFICS list. It casts only the 7th-house aspect; the special aspects belong to Mars, Jupiter and Saturn.
- Dignity: the dignity table has no rows for the nodes, so dignityOf() returns Neutral for Rahu in every sign. The BPHS Ch. 47 signs above are not applied.
- Lordship: Rahu rules no sign in SIGN_LORDS, but the Chara Dasha treats it as Aquarius's second lord beside Saturn.
- Timing: Rahu's Vimshottari period is 18 years (BPHS Ch. 46 Sl. 15).
One engine reading
For 19 January 1985, 11:14 IST, New Delhi, the engine places Rahu at 30.54 degrees sidereal - Taurus 0.54, Krittika pada 2, the 3rd house - and Ketu at Scorpio 0.54.
Pages that use this term
- Rahu in Vedic astrology - the full page on the node.
- Kaal Sarp Dosha explained - the Rahu-Ketu axis test and the mean-versus-true node check.
- Rahu Mahadasha - the eighteen-year period.
- Rahu in the 1st house - the first of the twelve house pages.
- Kaal Sarp Dosha calculator - reads every graha against the Rahu-Ketu axis.
Related terms
Chhaya graha, Kaal Sarp, Vakri and Rahu Kaal (a daily time window, not the node's position).