Drekkana, or D3, divides each 30° sidereal sign into three equal 10° parts. This guide explains the Parāśari sign assignment: the sign itself, its fifth sign, and its ninth sign. It is one named convention among several, so compare settings when results from two websites differ.
How the Parāśari sign mapping works
Begin with the D1 sidereal rāśi and count that sign as the first. A point from 0° inclusive to just below 10° remains in that sign. A point from 10° inclusive to just below 20° goes to the fifth sign, four signs forward. A point from 20° inclusive to just below 30° goes to the ninth sign, eight signs forward. All twelve signs use this same first, fifth, ninth pattern, yielding 36 D3 divisions around the zodiac.
| D1 degree in a sign | D3 destination | Gemini example |
|---|---|---|
| 0°–<10° | Same sign (1st) | Gemini |
| 10°–<20° | Fifth sign | Libra |
| 20°–<30° | Ninth sign | Aquarius |
The Bṛhat Parāśara Horā Śāstra, chapter 6 names the 1st, 5th, and 9th sign assignment. P. V. R. Narasimha Rao's Vedic Astrology: An Integrated Approach gives the same rule and a Gemini example. This site's code implements the arithmetic independently.
Boundary and degree examples
At 9°59′59″ Aries, the D3 sign is still Aries. At exactly 10° Aries, it becomes Leo; at exactly 20° Aries, it becomes Sagittarius. A position at 15° Aries sits halfway through the second 10° part and is displayed as 15° Leo in the derived D3 coordinate. At 30° Aries, the D1 sign becomes Taurus and its first D3 part begins in Taurus.
Mathematically, let s be the zero-based D1 sign index, and p be 0, 1, or 2 for the 10° part. The D3 sign index is (s + 4p) modulo 12. The position within that D3 sign is three times the degree inside the selected 10° part. This calculated D3 degree is a coordinate transform and should not be mistaken for a new sky longitude.
What the birth details change
The D3 Lagna is derived from the D1 ascendant. That angle depends on the birth time and coordinates. A date-only chart cannot identify it, and the tool requires a recorded local time, latitude, longitude, and the historical UTC offset that converts the clock reading to UTC. It flags points within 0.1° of a D3 boundary, where a small change in timing, ayanamsha, or ephemeris can switch the assigned sign.
The seven classical grahas and mean lunar nodes are calculated by this site's D1 method with Astronomy Engine 2.1.19 and an approximate Lahiri conversion. No Swiss Ephemeris table is imported. Birth dates are limited to 1800–2100, and historical time-zone lookup is not automatic. Compare the UTC instant, ayanamsha, node convention, and specific D3 system before treating a discrepancy as an error.
How this chart is used in the tradition
The Drekkana is often associated with siblings in Jyotish, as the Parāśara verse and commentary presented by SIA Vigyan explains. This page provides positions and a named mapping, without inferring the course of a relationship or an event. Other Drekkana systems exist; choosing one changes the coordinate scheme, so interpretations require that choice to be stated.
References
- Bṛhat Parāśara Horā Śāstra 6.6–10 — D3 divisions and first, fifth, ninth sign rule.
- P. V. R. Narasimha Rao, Vedic Astrology: An Integrated Approach — independently explained rule and Gemini worked example.
- SIA Vigyan D3 reference — source verse, sibling association, and convention.
- Astronomy Engine 2.1.19 — calculation library used by this site's D1 positions.