Birth input

Chart calculation needs a precise when and where. The shared BirthInput type is used by core.chart, vsop.ephemerides, and graph providers.

Core fields

Field	Role
`instant`	Birth moment as UTC (RFC 3339). Local civil time must be converted first — time-zones.
`latitude`	Geographic latitude, degrees (north positive). Sets local horizon for houses/angles.
`longitude`	Geographic longitude, degrees (east positive). With latitude, anchors the chart to the birthplace.

Optional fields

Field	Role
`house_system`	Defaults to Placidus when houses are computed. See house-systems-comparison (`WholeSign`, `Equal`, …).
`bodies`	Subset of `Planet` values; default includes Sun–Pluto and lunar nodes.
`ayanamsa`	Used for `calculate_sidereal` (default Fagan–Bradley in ephemeris config). Ignored for tropical `calculate`.

Without a reliable birth time

House cusps, Ascendant, and MC are uncertain (birth-time-accuracy). Planet signs from date-only instants may still be useful for outers; Moon and angles change quickly.

Quality checklist

Before calling the API: verify UTC conversion, coordinates, and documented time uncertainty — data-quality.