Western Synastry
asterwise_get_western_synastry
Aspect grid between two natal charts using the tropical zodiac. Returns all inter-chart aspects using standard inter-chart orbs. Useful for relationship compatibility analysis.
Parameters
| Parameter | Type | Required | Description |
|---|---|---|---|
person1 | object | yes | Birth data for Western astrology tools (tropical zodiac). Fields: date, time, lat, lon, person_name, timezone, house_system |
person2 | object | yes | Birth data for Western astrology tools (tropical zodiac). Fields: date, time, lat, lon, person_name, timezone, house_system |
response_format | enum: markdown, json | no |
What it covers
Bidirectional aspect matrix: every person1 planet to every person2 planet within orb. Does not produce a compatibility score — raw geometry only. House overlays are not included.
Workflow
BEFORE: asterwise_get_western_natal per person — understand charts individually first.
AFTER: asterwise_get_western_composite — midpoint chart for the relationship itself.
Input
person1, person2 — each WesternBirthData (date, time, lat, lon, timezone). house_system ignored for synastry payload.
Output contract
data.aspects[] — person1_planet, person2_planet, type, exact_angle, orb
data.total_aspects
Response format
response_format=json serialises the complete response as indented JSON.
response_format=markdown renders the same data as a human-readable report.
Both modes return identical underlying data.
Compute class
MEDIUM_COMPUTE (~600ms, two natal charts + aspect grid)
Errors
INVALID_PARAMS (local): WesternBirthData validation failures.
INTERNAL_ERROR: Any upstream API failure or timeout → MCP INTERNAL_ERROR
Do not confuse with
asterwise_get_western_composite — one merged midpoint chart vs synastry (two charts overlaid).
asterwise_get_western_compatibility — numeric 0–100 score vs raw aspects.
Connect
Remote MCP endpoint: https://mcp.asterwise.com/mcp. Authenticate with Authorization: Bearer <API key> or OAuth. See the MCP setup guide.