Ayana Bala plays a singular role in Shadbala calculation. Some see it as a part of Kala Bala, others see Ayana Bala as a separate source of strength.
Ayana Bala is identical to Cheshta Bala for the Sun (the Sun has no own Cheshta Bala because he is always in Sama motion).
Ayana Bala depends upon declination and the tropical zodiac, i.e. Ayanamsa must be neglected. Ayana Bala is the only source for evaluation of this planetary property. Moon and Saturn are strong with southern declination; Sun, Mars, Jupiter and Venus in the north.
Mercury plays a special role in so far as it is strong with northern as well as southern declination. So Mercury is again the most neutral planet.
All planets (including Mercury) have medium Ayana Bala near the equinoxes.
Ayana Bala depends upon the declination of the planets resp. their tropical longitude (which is nearly the same, see below). It is important to remember that Ayanamsa must be added to the planetary longitudes in Ayana Bala calculation.
The planets form 3 groups, each of them having their own rules for Ayana Bala calculation. All planets have 50% Ayana Bala strength (30 Virupas) in the equinoxes (0 Aries and 0 Libra).
The specific rules are
Kranti is the declination of a planet relative to the celestial equator. A planet in the equinox has Kranti zero while a planet near the point 0 Capricorn or 0 Cancer has maximum Kranti (which is about 23:27 deg).
The rule for Ayana Bala calculation is
ayanabala = 30 * ( eps +- kranti ) / eps = 1.2793 * (eps +- kranti)
where eps is the obliquity of the ecliptic (23:27). The rules for addition/subtraction of the Kranti value are
The second method is described by Parasara in chapter 27 (15-17) of Hora Shastra.
Find out the tropical longitude of a planet i.e. add Ayanamsa to its longitude. Calculate the distance from the nearest equinoxe. This value must be between 0 and 90. There are 3 Khandas (portions) for 3 possible Rasis: 45 (1st sign), 33 (2nd sign) and 12 (3rd sign).
1.) Planets within the 1st sign get the proportional strength according to their longitude in that sign (Khanda 45).
Example: A planet in 10° Pisces has distance 20° from equinoxe (0° Aries) and will get a value of 20/30 * 45 = 30.
2.) Planets in the 2nd sign (30°-60°) will get the Khanda of 45 plus proportional value (of 33) for their longitude in the 2nd sign.
Example: a planet in 10° Scorpio has distance of 40° from equinoxe. So the value is 45+ 10/30 * 33 = 56.
3.) Planets in the 3rd sign (60° - 90°) get a value of 78 (=45+33) plus the portion of the Khanda value (12).
Example: a planet in 15° Cancer has distance 75° from equinoxe. The total value will be 78 + 15/30 * 12 = 84.
The result must be between 0-90. Planets near the equinoxes get a small value (near 0); planets near 0°Cancer or 0°Capricorn get a high value (near 90).
Moon and Saturn get in addition 90 degrees if they are posited between Libra and Pisces. The value must be deducted from 90 if their position is between Aries and Virgo.
Same vice versa for Sun, Mars, Jupiter and Venus i.e. 90 must be added for for positions between Aries and Virgo; the value must be deducted from 90 for Libra to Pisces.
For Mercury 90 must always be added.
The result must be divided by 3 to get Ayana Bala in Virupas. The value must be between 0 and 60 Virupas.
This method doesn't use the declination of the planets but is only based upon their tropical longitude. The results are almost identical to the above described method's results.
The calculation rule is
ayanabala = 30 * ( 1 +- abs( sin( len ) ) )
where len is the tropical longitude of the correponding planet/luminary.
The rules for addition/subtraction are the same as above.
Take May 1st 1990 0:00 UT as example. Length must be Sayana (without Ayanamsa); declination must be relative to the equator (not to the ecliptic).
The table shows that the results are quite similar; the tolerance is within 2 Virupas.
|Planet||Length||Declination||Method 1||Method 2||Method 3|
|Sun||10°22 Taurus||14°56 N||49.1||48.8||49.4|
|Moon||29°55 Cancer||21°12 N||4.2||3.9||4.0|
|Mars||07°32 Pisces||10°12 S||17.0||18.8||18.5|
|Mercury||15°05 Taurus||17°36 N||52.5||50.5||51.2|
|Jupiter||06°57 Cancer||23°23 N||59.9||59.1||59.8|
|Venus||26°28 Pisces||02°29 S||26.8||28.2||28.2|
|Saturn||25°20 Capricorn||20°54 S||56.7||56.6||57.1|