Western

These operations return tropical positions of date: apparent longitudes on the ecliptic of that moment. They use the same ephemeris as the rest of the API, which is compared with JPL Horizons in Accuracy. The bodies are the Sun to Pluto and the true lunar node. Chiron and the asteroids are not included.

Houses

house_system can be placidus (the default), equal, whole_sign or porphyry.

• Placidus: a cusp is the ecliptic point whose hour angle is a set fraction of its own semi-arc. Above about 66° of latitude some points never rise or set, so Placidus is not defined there. We return an error that names the alternatives, and do not silently change the system.
• Porphyry: each quadrant between the angles is split into three equal arcs.
• Equal: each cusp is 30° on from the ascendant.
• Whole sign: each house is one sign, starting from the ascendant's sign.

With an unknown birth time, angles, houses and each planet's house are null. The chart is read at noon, so the Moon can be up to about 6° off.

Dignities

Domicile, exaltation, detriment and fall follow Ptolemy's scheme for the seven classical planets. Uranus, Neptune, Pluto and the nodes have none, because the modern rulerships are not agreed.

Aspects and orbs

Orbs differ between schools, so these are our defaults, and the response states them.

A major aspect with the Sun or Moon gets 2° more. Pass orbs to use your own, which also removes that extra. An aspect is applying when the gap from exact is closing.

Methods that are choices

• Composite: each point is the midpoint of the shorter arc between the two charts, and each cusp likewise. The other common method, the Davison chart, is not offered.
• Progressions: one day after birth for each year of life, using a year of 365.2422 days. The midheaven moves by the solar arc, and the ascendant follows from it at the birth latitude.
• Returns: the chart for the minute the Sun or Moon is back at its birth longitude, tropically. Give place for a relocated return. The Forecast tag has a sidereal solar return.

How it was checked

• Jupiter and Saturn at 0°29′ Aquarius at the great conjunction of 21 December 2020, against the published position.

• The Sun at 0°, 90°, 180° and 270° at the equinoxes and solstices that the ephemeris library's Seasons search finds.

• The ascendant on the eastern horizon and the midheaven on the meridian, using the library's own horizon calculation, at four latitudes on both sides of the equator.

• Every Placidus, Porphyry and equal cusp against its definition, typed separately in the tests.

• Solar returns against the library's SearchSunLongitude.

• All 576 house cusps of 12 made-up charts, in Placidus, Porphyry, equal and whole sign, against Swiss Ephemeris 2.10.03. The largest difference was under 0.01 of an arcminute, which is our rounding. The charts run from 1933 to 2045, between 64° north and 55° south.

Language

Set options.lang to hi for Hindi planet and sign names. The ids stay in English.