After I published my paper: Reconciliation of the Tropical and Sidereal Zodiacs I received many sincere questions. Here is one example:
Q: Do you find tropical signs more reliable in your practice?
Yes, I find tropical signs give a simpler, clearer picture more readily, if used with whole sign houses and sidereal nakshatras.
Q: Do you believe that Jyotish classics as ParasaraBHS, BrighuS and others are meant for tropical signs?
The classic textbooks on Indian Astrology (Jyotish) were written in different time periods. I believe that India has been using sidereal zodiac signs for a very long time – probably about 1800 or so years. Classics written after this time (c. 200 AD) were probably written in reference to the sidereal zodiac. But it is most important to note that about 500 years before and after that key point in history (c. 300 BC – 700 AD) there was practically no difference between tropical and sidereal zodiacs. And even for another 500 years or so on either side (800 BC – 1200 AD) the difference was not very dramatic. Most of the classics were written in this time frame. Therefore even if they were written by authors who had adopted sidereal zodiac signs, the practical difference between tropical and sidereal signs contemporary for those authors was negligible.
The fact that there are no significant “classics” much after this time frame is another evidence that Indian astrology began to lose it’s original potency as the sidereal zodiac became more and more out of phase with the true zodiac signs.
Q: Do the methods given in Jyotish classics work with tropical signs?
Yes, the methods defined in classics work best with tropial signs. In fact some of the methods defined in the classics cannot work at all without tropical signs. A case in point is the shad-bala system for calculating the potency of a planet. One component of this calculation is declination, which cannot be determined outside of tropical system (“declination” means the distance north or south of the equator).
Q: Do the classics not say simply what zodiac we should use?
Most of what we consider classic “astrology” textbooks do not, no. I address this in my paper. Calculation and interpretation are separate branches of Indian astrology. The Surya Siddhanta is the authoritative text on calculations. It does indicate that tropical planetary coordinates should be used. It instructs us to use ayanamsha is a means of converting sidereal calculations to tropical, and not visa versa as is now the fashion. The Srimad Bhagavatam also contains several chapters on astronomical phenomena and unequivocally defines the zodiac signs as tropical, and the nakshatras distinctly as sidereal.
I have addressed this much more completely in my paper.
Q: Are there not any old examples of charts indicating what zodiac system they use?
Classic Indian literature sometimes gives example charts, but not the birth data. For example they describe the planetary configurations for Rama and Krishna – but they do not say what birth data creates those charts. This is because the planetary configurations are themselves the most universal and reliable method of determining a point in time – so the ancient scriptures express the time of an important event such as the birth of an incarnation of God, by describing the planetary configurations.
However, since there is no second reference it is not possible to verify if the classics are describing the configurations in a sidereal or tropical reference. It is also particularly confusing because these configurations refer to points in time that are – by our pygmy modern conceptions and methods – extremely distant in the past and therefore very hard to verify by calculations – since over vast periods of time the speeds and motions of planets and the earth are not at all constant.