Polar latitude limitations in house calculation
What remains calculable when the Sun does not rise or set and some quadrant cusp systems have no conventional solution.
Calculation contract · released 2026-08-18
Definition
High-latitude geometry can remove daily rise/set events and make specific time-division house equations undefined, while the ecliptic and horizon still intersect.
Calculation procedure
Calculate each requested quantity independently, return null for absent solar events, detect unsupported cusp domains, and never substitute a house system without disclosure.
Required inputs
- Observer latitude
- Instant
- Requested solar event or house system
- Fallback policy
Maha convention
Maha’s conformance corpus includes polar solar-event cases and ascendant branch cases; whole-sign houses remain available when the ascendant is calculable.
Uncertainty and edge cases
A null sunrise is a valid geometric result, not missing data. A fallback UTC weekday or alternative house system must be labeled.
What this does not establish
Polar exceptions do not justify inventing an event time or forcing an auspiciousness score.
Authoritative references
These sources establish the calculation vocabulary, data product, or transformation convention. They do not establish astrological interpretation.
- Astronomy Engine
Don Cross (cosinekitty) · 2.1.19
Locally computed Sun and Moon positions derived from the VSOP87 and JPL-derived lunar theories, together with rise and set times, at the accuracy stated in the library documentation.
Boundary: Positions are computed in process rather than fetched from an authority, so a fact citing this source carries a digest over the computed values and not over a provider response body. Its accuracy is adequate for calendrical work and is not a substitute for a Horizons query where sub-arcsecond agreement matters.
- Swiss Ephemeris general documentation
Astrodienst AG · 2.10 documentation, checked 2026-08-18
An independent ephemeris implementation, supported reference choices, house calculations, and its dual-license boundary.
Boundary: Maha does not bundle or call Swiss Ephemeris in production. Frozen conformance results are validation evidence, not permission to redistribute its software or data.