Composite Charts (合成盤)
While synastry overlays two individual charts to see how they interact, the composite chart creates an entirely new, single chart that represents the relationship itself as a third entity — a new being with its own character, purpose, and challenges. The composite is the chart of the relationship, not the individuals.
How the Composite Is Calculated
The most common method (the midpoint composite) takes the mathematical midpoint between each pair of corresponding planets:
- Composite Sun = midpoint of Person A's Sun + Person B's Sun
- Composite Moon = midpoint of Person A's Moon + Person B's Moon
- And so on for all planets, Ascendant, and Midheaven
Example: Person A's Sun is at 10° Aries; Person B's Sun is at 20° Leo. The midpoint is 15° Gemini — the composite Sun is in Gemini, suggesting the relationship's core identity is communicative, curious, and intellectually oriented, regardless of what the individuals' Suns signify.
Interpreting the Composite
The composite chart is read similarly to a natal chart, but with a relational lens:
- Composite Sun: The relationship's core purpose and identity. What the partnership is for.
- Composite Moon: The emotional tone and daily rhythm of the relationship. How the partners feel together habitually.
- Composite Venus: The style of love and pleasure shared. What brings joy to the partnership.
- Composite Saturn: The structural challenges and commitments. Where discipline, limitation, or karmic work appears in the relationship.
- Composite Ascendant: How the relationship presents to the outside world. Its public face and social identity.
Composite vs. Davison Chart
An alternative to the midpoint composite is the Davison Chart (named after Ronald Davison), which calculates the actual date, time, and location midpoint between the two births and casts a real horoscope for that point in time and space. The Davison chart is considered more 'real' (it corresponds to an actual moment) and is preferred by some traditional astrologers for its connection to real astronomical data.
Practical Composite Reading
Key composite indicators to examine first:
- Composite Sun and its house: The relationship's central arena and purpose.
- Composite Moon sign and house: The emotional foundation.
- Saturn in the composite: Where commitment meets challenge.
- Planets in angular houses (1, 4, 7, 10): The most powerfully expressed relationship themes.
- Major aspect patterns: T-Squares in the composite indicate the relationship's central tension and growth edge.
Transits to the Composite
Current transiting planets aspecting composite chart planets describe the external forces acting on the relationship at any given time. Transiting Saturn conjunct the composite Sun (a multi-year influence for outer planets) describes a period of serious testing and restructuring of the relationship's core purpose — challenging, but often deepening.