1. WvA astrologers use house cusps defined by the intersections of ten planes of oblique ascension with the ecliptic plane. First the Ascendant Parallel Circle (APC) is constructed, a plane through the ascendant point, perpendicular to the celestial equator. In the diagram the APC is represented as the red elliptic dotted line.
2. The APC is then divided in six equal parts under, and six equal parts above the horizon. The division is represented in the diagram by red dotted lines, with numbers of cusps in black next to the division points.
3. Through the division points of the sixfold division six planes of oblique ascension are constructed. (position circle, green line) Only one of these planes is drawn in the diagram. Two of these planes are the horizon (black) and the meridian (black) planes. These planes define the ascendant, descendant, MC and IC. The intersections of the other planes (green) with the ecliptic (blue) define the other cusps.
The APC house system was developed by L. Knegt, and has been applied within the Werkgemeenschap van Astrologen (WvA) in the Netherlands since its establishment in 1947. The WvA is also known as the "Ram School".
- The Table of Houses for the APC system, made for the WvA.
- Cosmografie voor astrologen
- View the website of the Werkgemeenschap van Astrologen.