Ascendant labels and whole-sign house geometry
How one horizon intersection can yield different ascendant signs and therefore different whole-sign house assignments under parallel zodiac frames.
Frame comparison · released 2026-08-18
Shared fact substrate
The eastern intersection of the ecliptic and local horizon is one geometric direction for the declared instant, observer, and Earth-orientation convention.
Required shared inputs
- Resolved UTC instant
- WGS 84 observer coordinates
- Earth-rotation and obliquity method
- Tropical ascendant longitude
- Lahiri offset
Tropical view
The intersection receives a tropical sign label. Tropical whole-sign houses, if requested, count signs from that tropical ascendant sign.
Lahiri-sidereal view
The same tropical ascendant longitude is transformed by Lahiri. Jyotiṣa whole-sign houses count from the resulting sidereal ascendant sign.
Where they agree
Both views use the same observer and horizon geometry. They may agree on house numbers when the ascendant and target placement shift together, but this must be calculated rather than assumed.
Where they disagree
Ascendant sign, first-house boundary, house lords, and planet house assignments can differ. Different quadrant-house conventions introduce an additional disagreement not caused by zodiac frame alone.
Preservation policy
Record ascendant longitude before and after conversion, house-system identifier, and every house assignment inside the frame-specific namespace.
Prohibited synthesis
Do not combine a tropical ascendant with sidereal planetary signs or borrow house rulers across frames unless an explicitly named tradition rule requires that combination.
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.
- Astrology tradition registry
Maha Celestial
Named, versioned rule namespaces and the separation between source provenance and empirical support.
Boundary: A well-sourced traditional rule remains an unvalidated interpretive claim unless separately tested.