Argument:

Vic DiCara brings up the phrase “bhachakra-nabhau visuvat,” which he claims points to the equinox being the foundation of the zodiac.

Reply:

bhacakra-nābhau viṣuvad dvitiyam samasūtragam

ayana dvitayan caiva catasraḥ prathitāstutāḥ

Sūrya Siddhānta 14.7

If you don’t know the language (Sanskrit) – or if you are talking to people who don’t know it – then you can say “Vic is misinterpreting” or “claiming.” If you do know the language, however, you know Sūrya Siddhānta is simply, literally, directly, unequivocally  stating: 

The zodiac is a wheel turning on a hub
at the intersection of lines drawn
from equinox to equinox
and solstice to solstice. 

There could not be a more literal translation, nor is there any other description anywhere of the zodiac being a wheel that turns on the hub of anything else.

Argument:

In Vedic astrology, the equinox is used as a fixed starting point for the sidereal year, but the zodiac itself is anchored to the stars not the seasons. 

Reply:

Sūrya-Siddhānta just said the hub/anchor (nabhi) for the wheel of the zodiac (bha-cakra) is the equinox and solstices (viṣuva, ayana). Then you say, “The equinox defines the beginning, but the zodiac is really not anchored to it. It’s anchored to the stars.” It sounds exactly like your friend saying, “my car is a Honda,” and then you saying, “he has a car, but it’s not really a Honda.”

Besides directly contradicting Sūrya Siddhānta, you also contradicted yourself. How can the equinox be the starting point for the sidereal year, but not determine the start of the zodiac? Please do not embarrass yourself (and further contradict Sūrya Siddhānta 14.10) by claiming that the year is not identical to the zodiac.

Argument:

The 3rd Chapter of Sūrya Siddhānta demonstrates that it considers the zodiac to be sidereal.

Reply:

If this is correct, it would mean Sūrya Siddhānta contradicts itself, since it explicitly states that the zodiac is tropical (as discussed above).

However, there is no need to worry about that, because your argument is incorrect. The 3rd Chapter does not contain anything at all that would contradict its own explicitly tropical definition of the zodiac. This chapter discusses how to use a sundial to compare the current shadow with the equinoctial shadow to derive the Sun’s current zodiacal position, and from that derive other essential information like the current ascendant. The entire process is based on the Sun’s distance from the equinox, and thus only further confirms that the Sūrya Siddhānta uses a standard Tropical zodiac.

Argument:

Chapter 3 of the Surya Siddhanta, between text 40-50, provides a table showing the sidereal signs (Rasis) and their ascensional equivalents and oblique ascension values, which are tied to the ecliptic and horizon.

Reply:

I find no such table in chapter 3, nor anywhere in Sūrya Siddhānta. It is probably provided in someone’s commentary, not in the text itself (an important distinction). The section you refer to (3.40-50) is part of an extremely sophisticated mathematical instruction about how to accurately determine the Sun’s exact position on a given day, using the equinoctial shadow from a sun dial. Again, this only demonstrates that the equinox is the basis for measuring the zodiac, i.e. that the Zodiac is tropical.

Argument:

Nakshatras are anchored to the fixed stars and don’t depend on the shifting equinox. The precession accounts for a small shift over time in the alignment of the signs, but it doesn’t mean we’re suddenly using a tropical system. 

Reply:

This statement only reveals a lack of knowledge of what precession or ayanāṁśa really is. Frankly all of your arguments are like this, but I have tried to avoid saying so because it can be mis-interpreted as name-calling and bad manners which could invite the discussion towards emotional arguments, which we should avoid.

So yes, Nakshatra are indeed anchored to stars. In fact, that is why we need ayanāṁśa in the first place. The nakshatra are anchored to stars. The signs are anchored to solstice and equinox. Measurement by stars alone is approximate, but measurement by solstice and equinox (via sundial) is much, much more exact. Therefore, even to map planets to the nakshatra, we first figure out their tropical coordinates from the sundial, and then we convert this to sidereal coordinates via ayanāṁśa, so that we can accurately place the planets in their nakshatra.

Argument:

The fixed stars don’t change like the equinox, which is the key difference. 

Reply:

It is correct that the stars do not change positions relative to one another (at least their change is not noticeable on our human timescales). However, it is incorrect that the equinox changes. Neither the equinox nor the stars change positions. However, they do change their relationship to one another.

If this sounds confusing, just take two wheels. Spin them both, but spin one at a slightly different speed than the other. One of the wheels represents the zodiac anchored to the equinox and solstice, the other wheel represents the nakshatra anchored to certain key stars. Neither wheel changes its shape, but their relationship to each other slightly changes because their spin speed is slightly different.