See where your planets actually sit against the stars — not the seasons.
Free sidereal astrology chart with constellation boundaries, including Ophiuchus.
Sidereal astrology measures planetary positions against the actual star constellations in the sky, not the seasons. This accounts for precession — the slow wobble of Earth's axis that has caused a ~24° drift over the past 2000+ years.
When tropical astrology was created, 0° Aries aligned with the spring equinox and the constellation Aries. Today, the spring equinox occurs in Pisces. Tropical astrology stayed locked to the seasons; sidereal astrology stayed locked to the stars.
True sidereal vs. traditional Vedic: Traditional Vedic astrology uses Lahiri ayanamsa (equal 30° signs, shifted ~24° from tropical). True sidereal astrology maps to the actual constellation boundaries defined by the International Astronomical Union (IAU), which vary in size. This includes Ophiuchus, the 13th constellation the Sun passes through.
Our calculator shows both tropical and true sidereal positions so you can compare. Most people find their Sun sign shifts backward by one sign in sidereal — and ~6% discover they're Ophiuchus.
| Aspect | Tropical (Western) | Sidereal (Star-Based) |
|---|---|---|
| Reference Point | Spring equinox (seasonal) | Actual star constellations |
| Zodiac Structure | 12 equal 30° signs | 13 constellations, unequal widths |
| 13th Sign | Not included | Ophiuchus (Nov 30 - Dec 17) |
| Current Offset | Aligned to seasons | ~24° behind tropical |
| What It Measures | Psychological/archetypal timing | Physical star energy/astronomy |
| Vedic Astrology | Not used | Vedic uses sidereal + Lahiri (equal signs, no Ophiuchus) |
Both systems are valid — they just measure different cosmic phenomena. Tropical tracks Earth's seasonal cycle; sidereal tracks actual stellar positions.
A sidereal birth chart measures planetary positions against the actual star constellations, not the seasons. This accounts for precession — the 24° shift that's occurred since tropical astrology was created. Your sidereal chart shows where planets actually sit in the sky.
Traditional Vedic astrology uses Lahiri ayanamsa (equal 30° signs shifted ~24°). True sidereal astrology maps to the actual constellation boundaries defined by the IAU, including Ophiuchus as the 13th sign. Vedic is sidereal-based but uses different zodiac divisions.
Due to Earth's precession, the tropical zodiac (season-based) has drifted ~24° from the actual star constellations over 2000+ years. Most people find their Sun sign shifts backward by one sign in sidereal — and some fall in Ophiuchus.
They measure different things. Tropical tracks seasons and psychological archetypes. Sidereal tracks actual star positions and energetic astronomy. Neither is 'wrong' — they're different lenses. Our calculator shows both so you can explore what resonates.
Compare tropical, sidereal, draconic, Chinese astrology, and numerology — all in one chart.
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