A chapter in the Jyotiṣa lens
The Fork —
where the zodiac is nailed
to the sky.
Every kundli tool you have ever used offers a dropdown. Lahiri. Raman. Krishnamurti. Fagan-Bradley. Pushya-pakṣa. True Citrā. None of them tells you why the options are there, or what happens to your chart if you pick a different one. This chapter is that explanation. It is not about which is right.
The problemWhy there is a fork at all
A sidereal zodiac has to be nailed to something. The tropical zodiac has an obvious anchor — the equinox, the moment the Sun crosses the celestial equator — and it needs no argument. The sidereal zodiac claims to measure against the fixed stars instead, and there the trouble starts, because you must choose which star, and at what longitude to place it.
The reason the choice matters is precession. The Earth's axis wobbles, slowly, and the equinox drifts backwards against the stars at roughly fifty arcseconds a year — about one degree every seventy-two years, a full circuit in around twenty-six thousand. The gap between the tropical and sidereal zodiacs is therefore not fixed. It widens every year. That gap is the ayanāṃśa, and computing a sidereal chart consists, arithmetically, of one subtraction: take the tropical longitude, subtract the ayanāṃśa, and you have the sidereal position.
One subtraction. The entire dispute is about what number to put in it.
The schoolsWhat each one is committed to
The disagreement is not really astronomical. Everyone agrees about precession; the rate is measured and uncontroversial. The disagreement is about what the sidereal zodiac is anchored to, and each answer carries a different theory of what the zodiac is.
| School | Anchored to | The commitment underneath |
|---|---|---|
| Lahiri Citrā-pakṣa | Spica (Citrā) at exactly 180° | The zodiac is fixed by a single bright star named in the Indian tradition. Adopted as the national standard in 1956 on the recommendation of the Calendar Reform Committee, chaired by Meghnad Saha. Zero epoch around 285 CE. |
| Raman | A reading of Varāhamihira | The zodiac should follow what the classical Indian authorities appear to have used. Differs from Lahiri by roughly two degrees — the largest gap in common use. |
| Krishnamurti KP | A refinement of the Citrā anchor | Sub-divisional precision matters more than anything else, so the zero must be tuned to make the sub-lord scheme work. Zero epoch around 291 CE. Sits within about half a degree of Lahiri. |
| Fagan-Bradley | Reconstructed Babylonian norms | The zodiac should be calibrated against the framework the Babylonian astronomers actually used, since that is where it came from. The Western sidereal standard. About fifty-three arcminutes from Lahiri. |
| Galactic-centre schemes | The centre of the galaxy | A single star is arbitrary; the zodiac should be grounded in the structure of the galaxy itself. Astronomically motivated, internally coherent, and entirely modern — the galactic centre was not identified until the twentieth century. Later addition |
| Sūrya Siddhānta reading | A librating offset | Not steady precession at all but a trepidation — an oscillation back and forth within limits. A different model of the sky, not merely a different constant. Widely reported; the exact interpretation of the text is contested. |
There are roughly forty-two published ayanāṃśas. One of them is by P. V. R. Narasimha Rao — which is to say the author of the free tool whose dropdown started this argument is himself one of the people who added a line to it.
None of these is self-evidently correct, and no observation can settle it. The zero point of a sidereal zodiac is not a thing in the sky. It is a convention about how to read the sky, and conventions are chosen, defended and inherited — not discovered.
The consequenceWhat it costs a chart
It would be comfortable if the disagreement were academic. It is not. The ayanāṃśa is subtracted from every longitude in the chart, so every downstream result moves with it — and one of those results moves a great deal.
Viṃśottarī daśā is reckoned from the nakṣatra the Moon occupies at birth, and the fraction of that nakṣatra already traversed fixes how much of the first period has already elapsed. A nakṣatra spans 13°20′ — eight hundred arcminutes — and it carries the whole daśā period of its lord. For a Moon in a Venus-ruled nakṣatra, that is twenty years distributed across eight hundred arcminutes. Move the zero point and the entire timeline slides.
| Gap from Lahiri | Shift in the daśā |
|---|---|
| KP, older value — about 6′ | 16 to 55 days |
| KP, newer value — about 22′ | 60 to 201 days |
| Fagan-Bradley — about 53′ | 145 days to 1 year 4 months |
| Raman — about 2° | 11 months to 3 years |
The range in each row is the difference between a Moon in a Sun-ruled nakṣatra, whose lord takes six years, and one in a Venus-ruled nakṣatra, whose lord takes twenty.
And the structural effects are larger than the temporal ones. Shifting by the two degrees that separate Lahiri from Raman moves at least one graha into a different rāśi in about 46% of charts, and crosses a nakṣatra-pāda boundary — the unit the navāṃśa is built on — about 60% of the time.
Two competent astrologers, working carefully from the same birth data with the same software and different settings, are frequently not reading the same chart. Neither has made an error.
This siteWhy Lahiri, and what that costs
Turīya·Sūtra computes in Lahiri. There is no dropdown, and that is deliberate: a dropdown says pick one, we have no view, and we do have a view.
Lahiri is the Indian national standard. It is what the Indian Astronomical Ephemeris publishes, what Drik Panchang uses, and the default in essentially every mainstream Indian tool. Choosing anything else would put our charts at odds with every panchang a reader is likely to check, and the cost of that disagreement would fall on the reader rather than on us.
What the choice costs is worth stating plainly. It commits us to Spica as the anchor, and therefore to a particular answer to a question the tradition never settled. If the galactic-centre schools are right, we are about three degrees off. If Raman's reading of Varāhamihira is right, we are about two degrees off. We do not think either is more likely than the Citrā anchor, and we would not be able to prove it if we did.
So the honest position is this: the number in the subtraction is a choice, we have made it, we have said which one, and we have told you what it would cost if we are wrong. That is the most any sidereal system can offer, and rather more than a dropdown offers.
Corrections are welcome and will be published at support@turiya-sutra.in. The daśā-shift figures above are computed, not cited: nakṣatra span 800′ mapped across the full Viṃśottarī period of its lord, six years for the Sun through twenty for Venus. The boundary-crossing percentages assume uniform distribution of graha longitude, which is a simplification.