One celestial direction, two sign labels
Why a planet can receive different sign and degree labels while its physical direction, distance, speed, and observation time remain unchanged.
Frame comparison · released 2026-08-18
Shared fact substrate
Physical state vectors, apparent direction, direct or retrograde motion, and angular relationships remain facts about the same calculated moment.
Required shared inputs
- Frozen fact-bundle digest
- Tropical ecliptic longitude
- Longitude speed
- Lahiri offset
- Boundary-distance tolerance
Tropical view
The tropical sign is floor(normalized tropical longitude ÷ 30), with degree within sign measured from the corresponding equinoctial boundary.
Lahiri-sidereal view
The sidereal sign applies the same segmentation only after the named ayanāṁśa transformation, so a body may move to the preceding sign label.
Where they agree
The two records can agree on a sign when the transformed longitude remains inside the same named 30-degree segment, but that agreement is contingent rather than required.
Where they disagree
A sign disagreement is a coordinate-label disagreement. It propagates into sign-conditioned rules, dignity, rulers, and sign-based houses without changing the underlying body.
Preservation policy
Expose both normalized longitudes and labels with explicit namespaces such as tropical.sign and lahiriSidereal.sign; retain boundary sensitivity for each.
Prohibited synthesis
Do not describe a planet as simultaneously occupying an unlabeled hybrid sign or choose whichever sign yields the more compelling narrative.
What empirical comparison requires
Treat tropical and sidereal outputs as separate candidate models. Any performance claim requires preregistered features, outcomes, horizons, baselines, model-selection policy, multiplicity control, and prospective scoring that retains misses and abstentions.
Method sources
These sources define calculation and namespace policy. They do not determine which astrology system is true.
- Celestial fact-layer specification
Maha Celestial
The shared instant, observer, ephemeris, reference-frame, precision, software, and provenance fields from which both chart frames are derived.
Boundary: Reproducible celestial geometry does not validate an astrological interpretation.
- Lahiri ayanāṁśa calculations
Maha Celestial
Maha’s declared transformation from retained tropical longitude to a separate Lahiri-sidereal longitude.
Boundary: Selecting Lahiri defines one sidereal convention; it does not establish that sidereal astrology is superior or empirically valid.