Synastry & Composite Charts

Compare two natal charts for relationship analysis.

Synastry

Calculate aspects between two charts:

curl -X POST "https://api.astroapi.cloud/api/calc/synastry" \
  -H "X-Api-Key: your-api-key" \
  -H "Content-Type: application/json" \
  -d '{
    "dateTime1": "1990-06-15T14:30",
    "location1": {
      "latitude": 51.5074,
      "longitude": -0.1278,
      "timezone": "Europe/London"
    },
    "dateTime2": "1988-03-22T09:15",
    "location2": {
      "latitude": 48.8566,
      "longitude": 2.3522,
      "timezone": "Europe/Paris"
    }
  }'

Parameters

Parameter	Type	Required	Description
dateTime1	string	Yes	First person birth date/time in YYYY-MM-DDTHH:mm format
location1	object	Yes	First person location (longitude, latitude, timezone)
dateTime2	string	Yes	Second person birth date/time in YYYY-MM-DDTHH:mm format
location2	object	Yes	Second person location (longitude, latitude, timezone)
houseSystem	string	No	House system (default: "placidus")
language	string	No	Language code for text content (default: "en")
includeText	boolean	No	Include interpretation text (default: false)
includeReadableEntities	boolean	No	Include human-readable entity titles (default: false)
points	array	No	Celestial points to include in the calculation (see Available Points)
orbs	object	No	Custom orb values per aspect type

Response

{
  "data": {
    "type": "synastry",
    "attributes": {
      "aspects": [
        {
          "planet1": "sun",
          "chart1": true,
          "planet2": "moon",
          "chart2": true,
          "aspect": "trine",
          "orb": 2.3
        }
      ],
      "houseOverlays": {
        "chart1InChart2": {
          "sun": 7,
          "moon": 4
        },
        "chart2InChart1": {
          "sun": 10,
          "moon": 1
        }
      }
    }
  }
}

Composite Charts

Generate a composite (midpoint) chart:

curl -X POST "https://api.astroapi.cloud/api/calc/composite" \
  -H "X-Api-Key: your-api-key" \
  -H "Content-Type: application/json" \
  -d '{
    "dateTime1": "1990-06-15T14:30",
    "location1": {
      "latitude": 51.5074,
      "longitude": -0.1278,
      "timezone": "Europe/London"
    },
    "dateTime2": "1988-03-22T09:15",
    "location2": {
      "latitude": 48.8566,
      "longitude": 2.3522,
      "timezone": "Europe/Paris"
    }
  }'

Davison Chart

Calculate a Davison relationship chart (time-space midpoint):

curl -X POST "https://api.astroapi.cloud/api/calc/davison" \
  -H "X-Api-Key: your-api-key" \
  -H "Content-Type: application/json" \
  -d '{
    "chart1": { ... },
    "chart2": { ... }
  }'

Aspect Scoring

Get a compatibility score based on synastry aspects:

curl -X POST "https://api.astroapi.cloud/api/calc/synastry/score" \
  -H "X-Api-Key: your-api-key" \
  -H "Content-Type: application/json" \
  -d '{
    "chart1": { ... },
    "chart2": { ... },
    "weights": {
      "sun": 10,
      "moon": 10,
      "venus": 8,
      "mars": 7
    }
  }'