Synthesis uses 13 unequal sign bands, including Ophiuchus. This is not the equal-sign Lahiri zodiac.
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Synthesis uses 13 unequal sign bands, including Ophiuchus. This is not the equal-sign Lahiri zodiac.
Synthesis subtracts an offset of 31.38° + (birth year − 2000) / 72 from tropical longitude, then assigns one of 13 unequal sign bands. For 2026 the offset is 31.7411°.
In this model Virgo spans 49.7135°, Cancer 17.1488°, Scorpio 13.2273°, and Ophiuchus 12.3573°. Every planet receives the same angular offset; unequal band widths determine its resulting sign.
This is the Synthesis constellation-inspired model. It is not a calculation of the official two-dimensional IAU constellation boundaries. Lahiri uses a different offset and twelve equal 30° signs; its results can differ.
The calculator shows planetary positions before requesting a name or email. You can then continue to the full chart and optional interpretation. Comparing zodiac conventions does not establish that one predicts personality more accurately.
| Aspect | Tropical (Western) | Sidereal (Star-Based) |
|---|---|---|
| Reference Point | Spring equinox (seasonal) | Tropical longitude minus the Synthesis year-based offset |
| Zodiac Structure | 12 equal 30° signs | 13 custom sign intervals of unequal width |
| 13th Sign | Not included | Ophiuchus (≈ 2026-12-07 – 2026-12-18) |
| Current Offset | Aligned to seasons | 31.7411° (2026) |
| What It Measures | Planetary longitude within twelve equal 30° signs | Planetary longitude within Synthesis’s 13 unequal sign intervals |
| Vedic Astrology | Not used | Vedic uses sidereal + Lahiri (equal signs, no Ophiuchus) |
The same planetary positions are classified using different reference points and sign boundaries. Sidereal degrees here are measured from the start of each custom interval.
Once the calculator returns your chart you have two sets of positions for the same birth moment: tropical and true sidereal. The tempting question is which one is right. That is the wrong question. They measure different things, and the reading lives in the comparison. Take it in three passes.
Dates below are approximate for 2026. Near a boundary, use your full birth date, time and place. Ophiuchus is approximately December 7–18 in this model. There is no universal rule that everyone moves back one sign.
Synthesis subtracts an offset of 31.38° + (birth year − 2000) / 72 from tropical longitude, then assigns one of 13 unequal sign bands. For 2026 the offset is 31.7411°.
In this model Virgo spans 49.7135°, Cancer 17.1488°, Scorpio 13.2273°, and Ophiuchus 12.3573°. Every planet receives the same angular offset; unequal band widths determine its resulting sign.
The calculator shows planetary positions before requesting a name or email. You can then continue to the full chart and optional interpretation. Comparing zodiac conventions does not establish that one predicts personality more accurately.
Synthesis subtracts an offset of 31.38° + (birth year − 2000) / 72 from tropical longitude, then assigns one of 13 unequal sign bands. For 2026 the offset is 31.7411°.
This is the Synthesis constellation-inspired model. It is not a calculation of the official two-dimensional IAU constellation boundaries. Lahiri uses a different offset and twelve equal 30° signs; its results can differ.
The two systems use different reference points and sign boundaries. Synthesis subtracts its year-based offset and assigns the result to unequal intervals, so a placement may change sign. It does not always move back exactly one sign.
Neither convention establishes greater accuracy for personality or prediction. You can compare their symbolic interpretations, while checking the planetary calculations separately.
Compare the selected zodiac method first. Synthesis shows Tropical and its custom 13-sign Sidereal model together. Tools using Lahiri or another convention can assign different signs to the same birth moment. Match the time zone, coordinates and node convention when comparing results.
Yes. The full True Sidereal birth chart with all planetary positions, houses, and aspects is free at Synthesis. Optional paid readings ($28 one-time) provide a written multi-system analysis, but the chart math itself never sits behind a paywall.
Yes. “Natal chart” and “birth chart” both mean a chart for the moment of birth. This calculator’s Sidereal column uses the Synthesis custom 13-sign model; the word “natal” does not specify which zodiac convention another calculator uses.
Synthesis uses 13 unequal sign bands, including Ophiuchus. This is not the equal-sign Lahiri zodiac. In this model Virgo spans 49.7135°, Cancer 17.1488°, Scorpio 13.2273°, and Ophiuchus 12.3573°. Every planet receives the same angular offset; unequal band widths determine its resulting sign.
Your tropical Sun might be Capricorn while your sidereal Sun is Sagittarius. See both — across all five systems — and which one tracks closer to how you actually move through the world.
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