Getting Started

Computing Charts

engine.chart() accepts the calendar fields in UT, a latitude, a longitude (east positive), and either a house-system name or an options object.

Options

options.ts

const chart = engine.chart(
1990, 6, 10, 14, 30, 0,
27.95, -82.46,
{
  houseSystem: "koch",
  zodiac: "sidereal:lahiri",
  bodies: ["mean_lilith"], // extra bodies beyond the core set
},
);

The chart object

shape.ts

chart.bodies.sun.lon;        // ecliptic longitude, degrees
chart.bodies.sun.speed;      // degrees per day
chart.bodies.sun.retrograde; // boolean
chart.bodies.sun.sign;       // "Gemini"
chart.bodies.sun.ra;         // right ascension (true equinox of date)

chart.angles.asc;            // ascendant
chart.angles.mc;             // midheaven
chart.cusps;                 // twelve house cusps, degrees
chart.aspects;               // [{ a, b, aspect, orb }, ...]
chart.houseSystem;           // the system actually used
chart.houseSystemRequested;  // what you asked for (differs on polar fallback)

Local birth time to UT

The engine works in UT. Convert a local civil time with caelus-birth, which resolves the IANA zone from the location and applies historical tzdb rules.

birth.ts

import { toUT } from "caelus-birth";

const t = toUT({
year: 1990, month: 6, day: 10,
hour: 14, minute: 30,
lat: 27.95, lon: -82.46,
});

const chart = engine.chart(
t.year, t.month, t.day, t.hour, t.minute, 0,
27.95, -82.46, "placidus",
);

Edge and REST

The same engine runs on edge runtimes. The site exposes a demo endpoint: GET /api/chart returns a full chart as JSON.