Rahu Dasha

The Rahu Mahadasha is the period of the north node in the Vimshottari dasha, lasting eighteen years, the second longest of the nine. In the fixed sequence it follows Mars and precedes Jupiter. As the shadow graha of worldly desire, obsession, foreignness, and sudden amplification, Rahu in its dasha is traditionally read as a long and often turbulent season of ambition, unconventional pursuits, rapid rises and reversals, and engagement with the unfamiliar, its results shaped by Rahu's placement and its dispositor in the birth chart. The dasha a person begins life in is fixed by the nakshatra of the natal Moon. These are the interpretive conventions of the tradition; the Vimshottari system is a timing method keyed to the Moon's position at birth.

Rahu's eighteen years is the second longest mahadasha after Venus's twenty, and classical Jyotisha treats the lunar nodes, Rahu and Ketu, as chhaya grahas, shadow points rather than physical bodies, calculated from the intersections of the Moon's orbit with the ecliptic. Because a shadow point owns no physical sign in the way the seven visible grahas do, classical authorities have never fully agreed on Rahu's own sign, exaltation and mulatrikona assignments, with different texts and different regional schools of Jyotisha giving somewhat different tables; this disagreement over Rahu's essential dignity is a separate and older dispute from the Vimshottari period length itself, which all systems treat as fixed at eighteen years regardless of which dignity table is followed.

This period runs eighteen years of the 120 that the Vimshottari cycle divides among the nine grahas, and a life enters it at birth if the Moon stood in one of its lord's three nakshatras, Ardra, Swati and Shatabhisha.

The order of the nine periods is fixed and does not vary: Ketu, Venus, Sun, Moon, Mars, Rahu, Jupiter, Saturn, Mercury, and then Ketu again. It is the same order in which the nine grahas own the twenty-seven nakshatras, running three times through the list, which is what ties the dasha sequence to the Moon's position at birth. The nakshatra the Moon occupied gives the period a life begins in, and the fraction of that nakshatra already traversed gives how much of the period has already elapsed.

Each major period is subdivided in the same order and in the same proportions. A mahadasha is divided into nine antardashas, each running for the same fraction of it that its lord's own period bears to the whole 120 years, and the subdivision can be carried further into pratyantardashas and beyond. That is how the system produces timing fine enough to be tested: a combination in a chart is expected to show during the period and subperiod of the planets that form it.

Rahu holds eighteen years, second only to Venus. Rahu and Ketu are computed points rather than bodies, the two nodes of the Moon's orbit, and their inclusion among the period lords is one of the things that distinguishes this system from the Hellenistic material with which it shares a good deal else.