Cusp
The line where a house begins, given as a degree of ecliptic longitude.
The first house cusp is the Ascendant; the tenth house cusp is the Midheaven. Placing a planet in a house means finding which pair of cusps its longitude falls between.
One thing that's easy to get wrong: cusps wrap past 0°. A twelfth house running from 350° to 15° breaks any naive comparison — you have to normalise the cusp-to-point distance into a positive 0–360 span first. This wraparound bug is common in chart software, and it shows up as planets landing one house off.
Related
- HouseOne of twelve divisions of the sky, cut from your birth time and place, each covering an area of life.
- AscendantThe degree of the ecliptic rising over the eastern horizon at your moment of birth.
- Ecliptic longitudeThe angle along the ecliptic measured from the vernal point, 0 to 360° — the coordinate behind every position in a chart.