Chart points (ASC, DSC, MC, IC)

The four angles are the primary chart points in quadrant systems. They anchor the wheel and often rank with Sun/Moon in interpretive weight.

Ascendant (ASC) — 1st house identity

Ecliptic degree rising on the eastern horizon at birth.
Sets the “front door” of the chart in many schools; with Placidus, defines the 1st house cusp.
Changes sign roughly every 2 hours at mid-latitudes (faster at poles).

Descendant (DSC) — 7th house axis

Always ASC + 180° (mod 360) on the ecliptic — setting point on the western horizon.
Partnership / “other” axis in many traditions; 7th house cusp in quadrant systems.

Midheaven (MC) — career / public axis

Ecliptic point where the local meridian meets the ecliptic above the horizon (culmination).
In Placidus, equals 10th house cusp; in Whole Sign or Equal, may sit inside another house slice (house-systems-comparison).

Imum Coeli (IC) — roots / private axis

MC + 180° — meridian below the horizon (nadir).
4th house themes in quadrant work; cusp in Placidus is the IC.

Output shape

core.chart returns house cusps and cross longitudes in the natal DTO (via chart_to_dto). Graph wheels in other providers consume the same longitudes for drawing.

References

See also chart-angles, houses, birth-input.