The formulas behind Jyotishya

Jyotishya is a science project: it applies traditional rules exactly and shows the working, without interpreting the results. These notes give each rule's definition, formula and a worked example.

• Chandrashtama: the Moon in the 8th sign from the natal Moon
  Chandrashtama is the rule for when the transiting Moon is in the 8th sign from your natal Moon. The formula, a worked example, and how Jyotishya scores it.
• Tara bala: the nine-tara count from the birth nakshatra
  Tara bala counts from your birth nakshatra to the day's nakshatra and takes the remainder mod 9. The formula, the nine taras, their scores and a worked example.
• North Indian and South Indian kundali charts
  The same birth chart in two layouts: the North Indian diamond keeps houses fixed, the South Indian grid keeps signs fixed. How each is drawn, step by step.
• Why Vedic and Western signs differ: the ayanamsa
  Vedic astrology uses the sidereal zodiac and Western the tropical one, about 24° apart. The cause (precession), the formula and how to convert a position.
• Vimshottari dasha: calculating the planetary periods
  Vimshottari dasha divides a 120-year cycle into nine planetary periods set by the Moon's nakshatra at birth. The sequence, the lengths and the balance formula.
• The Navamsa (D9) chart: the calculation
  The Navamsa divides each sign into nine parts of 3°20' and maps each part to a sign. The starting-sign rule by sign type, a worked example and vargottama.
• BaZi (Four Pillars): the calendar calculation
  BaZi expresses a birth moment as four stem-branch pairs for year, month, day and hour. How each pillar is calculated, with the solar-term and 60-day rules.