Planet positions

A natal body snapshot (Sun, Moon, Mercury, …) typically includes:

Ecliptic longitude (and latitude when computed)
Tropical or sidereal sign and degree within the sign
House number when birth time and houses are known
Optional speed / retrograde for interpretation

Default bodies

astrorust_core::Planet::DEFAULT_CHART_BODIES: Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, North Node, South Node, Uranus, Neptune, Pluto. Override via BirthInput.bodies. Nodes: lunar-nodes.

Geocentric frame

Positions are geocentric ecliptic — standard for horoscope software (geocentric-vs-topocentric). Outer planets move slowly; Moon and angles change rapidly (birth-time-accuracy).

Provider flow

VSOP (+ Moon model) → λ → sign/degree → house from cusps

Tropical: core.chart / calculate
Sidereal: calculate_sidereal (longitude field replaced with sidereal λ)

Uncertainty

Sign placement is usually robust; lunar arcminutes and angles may differ from DE/Swiss almanacs — ephemeris-uncertainty, vsop87.