There are 27 constellations in the zodiac divided into nine groups. Every three groups are ruled by one planet:
1. Aswini, Makha and moola are ruled by Ketu.
2. Bharani Pubba and porvashad are ruled by Venus.
3. Krittika, Uttara and Uttarashada are ruled by Sun.
4. Rohini, Hasta and Sravana are ruled by Moon.
5. Mrigasira, Chitta and dhanista are ruled by Mars
6. Aridra, Svati and Satbhishak are ruled by Rahu.
7. Punarvasu, Vishakha, and poorva bhadrapada are ruled by Jupiter.
8. Pushya, anuradha and Uttara Bhadrapad are ruled by Saturn.
9. Aslesha Jyeshta and Revati are ruled by Mercury
To Moons motion the period of a dasa left over by calculating the balance portion to be moved the dasa at birth be worked out.
An example
A child as born in Aswini star in 3rd pada at 10 degree of Aries. The 7 years of Ketu = 13 degrees and 20 minutes = 800 minutes. Moon has passed 10 degree = 600 minutes. So the balance is 200 minutes to be passed. 200x 7 = 1400 / 800 = 14/8 = 1.75 ears or 1 years and 9 months.
A planet can be an Excellent benefic called as the Yoga karaka, or a benefic, or a neutral, or a malefic or dire malefic to an ascendant depending on its nature and ownership of Houses. Generally planets owning Quadrants and trines are benefics. Those owning Houses 3, 6, 8 and 12 are malefic. Owners of 2nd and 11th are classified according to their company.
The tabulated form of this classification if given below:
Each of the Major period is further sub divided into nine sub periods., each sub lord gives good or bad results depending on its relation with the major lord and also the ascendant lord or the ascendant lord and the sub lord is adverse but the concerned planet itself is a benefic then the results are neutral. If the relation between the Major Lord and sub lord is good and sub lord happens to be a benefic then the results are excellent. If both major and sub lords are adverse then the result will be very bad. In a bad Dasa and antara if the transit of Jupiter and Saturn are also adverse the result can be disastrous culminating in the death of native also.
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