Calculationdraftschool: jyotisha· Frawley — Astrology of the Seers

How to calculate the Vedic chart (from a Western Tropical chart)

rāśi-cakra-gaṇana

also: vedic-chart-calc, rashi-chakra-calculation

cal-vedic-chart-calculation

Definition

The procedure for producing a Vedic (sidereal) chart: compute the Western Tropical chart by ordinary methods, then SUBTRACT the appropriate Ayanamsha from all planetary and sign positions. Any Western chart thereby converts to a Vedic chart. The traditional Indian method (depending on the time of dawn etc.) is more complicated and unnecessary. Caveats: Western planetary ASPECTS do not carry over (Vedic aspects differ); and Western house CUSPS mark the MIDDLE, not the beginning, of the Vedic house. The chart is read not only from the Ascendant but also from the Moon and other planets (favouring the South-Indian square "Rashi Chakra" diagram over the North-Indian diamond). Frawley's worked sample is Mahatma Gandhi's chart; the Vedic system de-emphasizes the Sun sign, weighting the Ascendant and Moon.
Modern

Prāṇa relevance

Prāṇa relation not yet traced — a complete, acceptable terminal state.

Connections (2)

derived-from · 1
  • →Sidereal vs Tropical zodiac — Frawley's position (Vedic astrology is sidereal)Modern
    The Vedic-chart procedure (subtract the Ayanamsha to convert a Tropical chart to a Vedic one) is the direct operational consequence of the sidereal-vs-tropical position: because Vedic astrology uses the SIDEREAL zodiac (signs = 30° sections of the actual fixed stars, precession tracked) while Western astrology uses the TROPICAL zodiac (0° Aries = vernal equinox), the two differ by exactly the Ayanamsha, and the conversion procedure follows from that doctrine. The calculation is derived from the zodiac-choice rule.
prerequisite-of · 1
  • ←Ayanamsha (the sidereal–tropical correction)Modern
    To produce a Vedic (sidereal) chart one computes the Western Tropical chart and then SUBTRACTS the appropriate Ayanamsha from all planetary and sign positions (Vedic position = Tropical position - Ayanamsha). A chosen Ayanamsha value is therefore a strict prerequisite of the chart calculation: the cal-vedic-chart-calculation procedure explicitly lists 'a chosen Ayanamsha (cal-ayanamsha)' among its prerequisites and cannot run without it.

Sources

  • txt-frawley-astrology-seersHow to Calculate the Vedic Chart (book pp.53–54)Modern✓ verifiedsubtract the Ayanamsha from the Western chart; Indian dawn-based method unnecessary; aspects don't carry over; cusps = house-middles; South-Indian Rashi Chakra preferred; Gandhi sample; Ascendant/Moon weighted over Sun sign

Other attributes

Formula
Vedic position = Tropical position − Ayanamsha (for every planet and the sign/house framework)
Divisor
n/a
Remainder Interpretation
n/a — a wholesale offset, not a modular operation
Prerequisites
an accurate Western Tropical chart; accurate birth data; a chosen Ayanamsha (cal-ayanamsha)
School Variants
Diagram styles: South-Indian square chart (fixed sign positions, Aries at the upper-centre star, signs clockwise — preferred, since houses are read from multiple reference points) vs North-Indian diamond. Vedic astrology has many more calculations than Western, so a computer program is 'almost essential'.
Notes
ATTRIBUTE-HARVEST: the procedure is captured as one calculation entity holding the steps/caveats; prerequisite-of edge to chart-reading is implicit. Depends on cal-ayanamsha (prerequisite).
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