Relationship Charts (關係合盤)

The Composite & Davison Charts — a Relationship as Its Own Being

Overview

Where synastry compares two people's separate charts to map their chemistry, a relationship chart treats the RELATIONSHIP itself as a single entity with its own chart. There are two classic ways to build one. The Composite chart takes the midpoint of every point in the two natal charts — the composite Sun is the midpoint of the two Suns, the composite Moon the midpoint of the two Moons, and so on — producing a symbolic 'third chart' that describes the bond rather than either partner. The Davison chart (also called the Davison Relationship Chart) does something different and remarkable: it casts a REAL chart for the exact midpoint in time between the two births and the geographic midpoint between the two birthplaces, so the relationship gets a genuine 'birth moment' with unambiguous, real angles. askTIAN computes both from two sets of birth data.

Origin & history

The midpoint composite chart was popularised by the American astrologer Robert Hand in his 1975 book 'Planets in Composite: Analyzing Human Relationships', still the standard reference. The technique itself grew out of the mid-twentieth-century midpoint tradition (Cosmobiology, the Hamburg School), which treated the midpoint of two bodies as a sensitive point of blended meaning. The Davison chart is named after the British astrologer Ronald C. Davison, who introduced the time-and-space midpoint method as an alternative that yields a real, castable chart rather than a purely symbolic one — sidestepping the composite chart's long-debated question of how to derive its Ascendant.

The two methods are complementary and often used together. The composite chart is the more widely taught, but it carries one genuine ambiguity: its Ascendant. Some astrologers take the midpoint of the two Ascendants directly (simple, but the resulting Asc and Midheaven are usually not the 90-degrees-apart that a real chart requires); Robert Hand preferred to derive the Ascendant from the composite Midheaven using the midpoint of the two birth latitudes, keeping the angles geometrically consistent. askTIAN returns BOTH so the difference is visible. The Davison chart has no such ambiguity — because it is a real moment and place, its angles are simply real — which is exactly why many astrologers cross-check the composite against it. askTIAN's Davison engine reproduces the defining arithmetic exactly: the chart's instant is the mean of the two birth instants, and its place is the great-circle midpoint of the two birthplaces.

How it works

Provide two people's birth data — date, and (for the angles) time, timezone and place. For the Composite chart, the engine computes each person's natal positions on the shared tropical ephemeris, then takes the circular short-arc midpoint of each planet (and, when both birth times and places are given, of the Ascendant and Midheaven), and finds the aspects among the composite points. For the Davison chart, it averages the two birth instants into a single real Julian day, finds the great-circle midpoint of the two birthplaces, and casts a normal chart for that moment and location — real planets, real Ascendant, real Midheaven. Each chart also gets a transparent 0–100 'ease' tally of its harmonious versus hard aspects (a reflection aid, never a verdict on the relationship). Birth times and places are needed for the angles; without them the planetary midpoints still compute.

Good for

• Reading a relationship as an entity in its own right
• The composite Sun, Moon and Ascendant — a couple's shared purpose, feeling and face
• The Davison chart — the relationship's real 'birth moment' and place
• Comparing the two methods (midpoint vs Hand's derived Ascendant)
• A deeper layer beneath basic synastry
• Business partnerships, friendships and family bonds, not only romance

Use cases

Composite Chart

Send two births and receive the composite planets, both Ascendant methods (midpoint and Hand's derived), the Midheaven, the internal aspects and an ease tally — the symbolic 'third chart' of the bond.

Davison Relationship Chart

Get the relationship's real virtual-birth moment (UT) and great-circle midpoint place, with real planets, Ascendant and Midheaven — a chart you can read like any natal chart.

Composite vs Davison Cross-Check

Compare the symbolic composite against the real Davison chart; where they agree, a theme is doubly emphasised; where the composite Ascendant is uncertain, the Davison angles resolve it.

Any Two-Person Bond

The techniques apply to any pair — partners, co-founders, friends, parent and child — wherever it helps to see the relationship as its own thing.

Key terms

Composite Chart

A symbolic chart in which every point is the circular midpoint of the two people's corresponding points (composite Sun = midpoint of the two Suns, etc.). Describes the relationship, not either partner.

Davison Chart

A real chart cast for the exact midpoint in time between the two births and the geographic midpoint of the two birthplaces — the relationship's own 'birth moment', with unambiguous angles.

Midpoint (near arc)

The short-arc midpoint of two zodiac longitudes; when the two points straddle 0° Aries, the midpoint is taken across the short way (so 25° Pisces and 5° Aries midpoint to 0° Aries, not 0° Libra).

Composite Ascendant

Method-dependent: either the midpoint of the two Ascendants, or (Robert Hand) derived from the composite Midheaven at the midpoint latitude so the angles stay 90°-consistent. askTIAN returns both.

Ease score

A transparent 0–100 tally of a chart's harmonious versus hard aspects, offered as a reflection aid — never a prediction of whether the relationship succeeds.

API

The askTIAN Relationship Charts endpoint takes two people's birth data and returns both the Composite (midpoint) chart and the Davison (time-space midpoint) chart. The Composite gives every planet's midpoint position, the Ascendant by BOTH the midpoint method and Robert Hand's derived reference-place method, the Midheaven, the internal aspects and a transparent 0–100 ease tally. The Davison gives the relationship's real virtual-birth moment (UT), the great-circle midpoint place, and a real chart with genuine Ascendant and Midheaven. Tropical and geocentric on the shared Meeus ephemeris; birth times and places are needed for the angles, and the planetary midpoints compute without them. A best-effort LLM reading is returned in parsable sections (set interpretation:false for structured data only). Honest rails: a symbolic reflection on a bond, not a predictor of whether it lasts; the composite Ascendant is method-dependent (both given); not medical, legal or financial advice.

Endpoint: POST /trpc/composite.chart — 6 TIAN Points. See the API documentation and Playground.