Comparison
Tropical vs Sidereal Zodiac
Two ancient coordinate systems, ~24° apart. Not a fight - a different question about the same sky.
The 24° difference
The offset between the two zodiacs is called the ayanamsa. Astreya uses the Lahiri ayanamsa (~24° in 2026) - the official standard of the Indian government and modern Jyotish.
FAQ
What's the difference between tropical and sidereal zodiac?
The tropical zodiac starts at 0° Aries = the spring equinox, moving with Earth's seasons. The sidereal zodiac starts from the fixed stars. Because of the ~25,800-year precession of the equinoxes, the two systems currently differ by about 24° (the Lahiri ayanamsa).
Which one is 'correct'?
Both are internally consistent - they answer different questions. Tropical (Western) astrology reads seasonal archetypes; sidereal (Vedic / Jyotish) astrology reads stellar positions. Astreya calculates and offers both.
Will my Sun sign be different?
Very likely. In the sidereal (Lahiri) system your Sun typically moves back one sign - for example a tropical Aries becomes sidereal Pisces. The Moon and rising sign also shift.
Which does Astreya use?
The Western modules (natal, transits, synastry, tarot support) use tropical + Placidus. The Vedic module uses sidereal (Lahiri) + Whole Sign houses. Both are computed from the same Swiss Ephemeris data.