Relationship Charts

Astrology offers three distinct methods for analyzing the dynamics between two people. Each approach answers a different question about the relationship.

Synastry

Question: How do these two individuals affect each other?

Synastry overlays one person's chart onto another's and examines the inter-chart aspects — the angular relationships between bodies in chart A and bodies in chart B. If person A's Venus conjuncts person B's Mars, that tells you something about the dynamic between them.

Synastry preserves each person's individual chart. You get two complete natal charts plus the inter-chart connections. It's the most common technique for relationship analysis.

API endpoint: /v1/synastry (3 credits)

Composite chart

Question: What is the nature of the relationship itself?

A composite chart creates a single chart by computing the midpoint of each pair of corresponding positions. The composite Sun is the midpoint between person A's Sun and person B's Sun. The composite Moon is the midpoint of the two Moons. And so on for every body and house cusp.

The result is a synthetic chart — it doesn't represent a real moment in time, but rather a mathematical abstraction of the relationship. It's interpreted like a natal chart, but as the chart of the relationship rather than a person.

Midpoint resolution

When two planets are at 10° and 200°, there are two possible midpoints: 105° (nearest) and 285° (far). Most astrologers use the nearest midpoint (the default), but the resolution parameter lets you choose.

API endpoint: /v1/composite (3 credits)

Davison chart

Question: What does the relationship look like as a real chart?

The Davison chart (created by Ronald Davison) computes the midpoint in both time and space between two births, then casts a real natal chart for that moment and location. If person A was born June 15, 1990 in New York and person B was born March 22, 1988 in London, the Davison chart is a real chart cast for approximately May 3, 1989 at a point in the mid-Atlantic.

Unlike the composite chart, the Davison chart represents actual astronomical positions at an actual moment. This means it can be progressed, directed, and used with transits — techniques that don't work with composite charts because composites aren't tied to a real time.

API endpoint: /v1/davison (3 credits)

Choosing a technique

Most astrologers use synastry and composite together. The Davison chart is used when timing matters — transits to the Davison chart can indicate when relationship events occur.