Sidereal Birth Chart — Your Chart Against the Actual Stars
If you already have a western birth chart and someone has told you your "real" sign is different, this is the calculation behind that claim — and it is a real astronomical offset, not a gimmick. Your chart is computed sidereally with the Lahiri ayanamsa, and you can see exactly which placements move and which do not.
What sidereal actually measures
Both systems divide the sky into twelve 30° signs. They disagree about where to start counting.
Tropical astrology anchors 0° Aries to the March equinox — the Sun's position at the moment spring begins in the northern hemisphere. It is a seasonal zodiac, tied to the Earth's relationship with the Sun.
Sidereal astrology anchors the zodiac to the fixed stars. It is a stellar zodiac, tied to where the constellations actually are.
The Earth's axis wobbles, completing a circuit roughly every 26,000 years. That is axial precession, and it means the equinox point drifts backwards against the constellations at about 50 arcseconds a year. The two zodiacs coincided around the third century CE. They are now about 24 degrees apart.
That offset is the ayanamsa. Several values are in use; Lahiri is the Indian government standard and the one Vedic astrology overwhelmingly means. It is what is used here.
Which of your placements change, and which do not
The 24-degree shift is close to a full sign, so the effect is large but not uniform, and it is worth knowing what to expect before you compare charts.
Your sign usually moves back one. Around 80% of people get a different Sun sign sidereally. If your tropical Sun sits in the first 24 degrees of a sign, it moves to the previous one; only births in the last few degrees stay put. A tropical Leo is most often a sidereal Cancer.
Every planet shifts by the same amount. The ayanamsa is a single offset applied to the whole zodiac, so the *relationships* between planets are untouched. Your conjunctions, oppositions and trines are identical in both systems — aspects are angular distances, and subtracting 24 degrees from both ends changes nothing.
Your houses may or may not move. The ascendant shifts by the same 24 degrees, so it usually changes sign too. But Vedic astrology conventionally uses whole-sign houses, where the ascendant's whole sign is the first house, rather than the Placidus system most western charts default to. That is a second, separate difference, and it is often the bigger one in practice.
Your nakshatra is new information. Sidereal astrology subdivides the zodiac into 27 nakshatras of 13°20' each. There is no tropical equivalent, and your Moon's nakshatra is what the entire Vimshottari dasha timeline is computed from.
Is one of them right?
Not in a way that can be settled by argument, and anyone who tells you otherwise is selling something.
The honest version: they measure different things and were designed to. Tropical tracks the seasonal year, which is why it works the way it does for a temperate-hemisphere calendar. Sidereal tracks the stars, which is what the Indian tradition has always done, and it is also what carries the machinery — nakshatras, dashas, divisional charts — that has no tropical counterpart.
The practical rule is simply not to mix them. Read a sidereal chart with sidereal techniques. A tropical Sun sign interpreted against a Vimshottari dasha timeline is two systems' outputs stapled together, and the result means nothing in either.
What you can check, and should: run your birth details through two tools that both claim sidereal calculation and compare the ascendant degree. It is the most time-sensitive value in the chart. If they agree, both are computing. If one is vague about its ayanamsa, it may not be.
The full sidereal reading is the Detailed Kundli Report
Your ascendant and its lord, all nine grahas by dignity, the twelve houses and where their lords went, your Moon nakshatra and the full Vimshottari dasha timeline with real dates, the D-9 and D-10, and the yogas and doshas actually present in your chart. Computed with the Lahiri ayanamsa off Swiss Ephemeris, 30+ pages, delivered as a PDF.
Every life domain plus your decade-by-decade dasha roadmap. Most buyers upgrade here after their first report. ₹3999.
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