Geometric, astrometric, and apparent positions
Three position types that can carry different correction sets even when they share a coordinate frame.
Calculation contract · released 2026-08-18
Definition
Geometric positions omit light propagation; astrometric positions account for light time in a specified frame; apparent positions add observer-oriented effects such as aberration and deflection according to the model.
Calculation procedure
Choose the position type before calculation, record each applied correction, and compare results only when origin, frame, epoch, and correction state match.
Required inputs
- Target and observer
- Instant and timescale
- Reference frame
- Requested correction model
Maha convention
Maha labels production natal placements as apparent geocentric ecliptic longitudes of date and carries that wording into methodology output.
Uncertainty and edge cases
The terminology is provider-specific unless its exact correction contract is preserved.
What this does not establish
“Apparent” does not mean visually observable or astrologically effective.
Authoritative references
These sources establish the calculation vocabulary, data product, or transformation convention. They do not establish astrological interpretation.
- Horizons System Manual
NASA/JPL Solar System Dynamics · 4.98d (2025-11-21)
Solar-system object identifiers, observing centers, time inputs, reference frames, corrections, output quantities, and stated ephemeris limitations.
Boundary: Horizons output is authoritative only with the complete query contract preserved; transformed or rounded values require their own provenance record.
- SPICE Reference Frames
NASA/JPL Navigation and Ancillary Information Facility · 2021-12-31 revision
Frame identifiers, frame centers, transformations, orientation relationships, and the distinction between frames and coordinate representations.
Boundary: A frame name alone does not establish the observing origin, epoch, equinox, time scale, or correction model.