Sukuyo and nakshatra: why lunar mansions can differ
Sukuyo and nakshatra use lunar-mansion terms, but date-table and longitude-based results are not interchangeable; compare inputs, zodiac, and assignment rules.
Overview
Record the birth-time precision and sidereal setting of the comparison. A shared lunar-mansion tradition does not establish an identical modern algorithm.
At a glance
- Sukuyo here
- Lunar month/day lookup
- Nakshatra comparison
- Sidereal longitude assignment
- Do not assume
- Identical personal result
Shared vocabulary is not a shared algorithm
Both traditions discuss lunar mansions, but historical connections do not make every modern procedure the same.
Start with the actual calculation described by each tool.
Compare the input precision
The Sukuyo product uses a birth date without a birth time. A precise lunar longitude requires a suitable instant.
A date-only label cannot recover the missing degree.
Compare zodiac conventions
For a sidereal nakshatra result, record the ayanamsha and other relevant calculation settings.
Do not treat an unnamed sidereal convention as equivalent to every other one.
Compare subdivisions
The Sukuyo four-foot reference can list possible spans while leaving a personal foot unresolved.
A nakshatra pada computed from longitude is a different result with different evidence requirements.
Explain disagreement honestly
Keep both system labels and inputs beside the results. Different answers may follow from different definitions rather than an arithmetic fault.
Do not force agreement by shifting the birthday or silently changing the zodiac origin.
Create a disagreement receipt
For Sukuyo, save civil date, lunisolar result, month-start table and mansion. For nakshatra, save timestamp, timezone, lunar longitude, ayanamsha, boundaries and result.
The first differing definition explains why matching names are not required; whichever description feels closer cannot validate the omitted calculation fields.
Sources and editorial basis
- 宿曜經 · T1299 卷上卷上「分定宿直品第一」: mansion and foot reference; exact modern sidereal assignment requires separately declared settings.Historical text for mansion names and calendar tables. Its table is not identical to OpenFate’s modern 27-mansion lookup; it does not establish predictive validity.
- OpenFate Sukuyo calculator and calculation conventionEditorial code check 2026-09-10, policy 1.0.0: nakshatra; policy.ts, constants.ts, engine.ts and traditional-cycles.ts. Product settings are not an independent historical authority; practical examples are OpenFate editorial applications.Product-specific input and output reference. Editorial checks also inspected policy 1.0.0 and the month-start constants on 2026-09-10; those implementation checks are not an independent traditional authority.
- Swiss Ephemeris: Sidereal Ephemerides for AstrologySwiss Ephemeris documentation §2.8.1 The problem of defining the zodiac: tropical/sidereal origins and ayanamsha; §2.1 planetary and lunar ephemerides.Technical reference for tropical/sidereal frames and ayanamsha choices. Longitude calculation and symbolic interpretation remain separate.