Synastry

The POST /v1/synastry endpoint compares two natal charts: it calculates cross-aspects between planets of both people and returns a compatibility score. Cost: 50 credits (Tier 3).

Request parameters

Two nested objects chart1 and chart2, each with the same parameters as /v1/chart:

Parameter	Type	Required	Description
chart1	object	Yes	First person’s data
chart2	object	Yes	Second person’s data

Each object: date, time, timezoneOffset, latitude, longitude, houseSystem, name, city.

Example request

cURL

curl -X POST https://api.astroway.info/v1/synastry \
  -H "X-Api-Key: aw_live_your_key_here" \
  -H "Content-Type: application/json" \
  -d '{
    "chart1": {
      "date": "1990-07-14",
      "time": "14:30:00",
      "timezoneOffset": 3,
      "latitude": 50.4501,
      "longitude": 30.5234,
      "name": "Person A"
    },
    "chart2": {
      "date": "1992-03-22",
      "time": "09:15:00",
      "timezoneOffset": 2,
      "latitude": 48.8566,
      "longitude": 2.3522,
      "name": "Person B"
    }
  }'

Node.js

const body = {
  chart1: { date: '1990-07-14', time: '14:30:00', timezoneOffset: 3, latitude: 50.4501, longitude: 30.5234, name: 'Person A' },
  chart2: { date: '1992-03-22', time: '09:15:00', timezoneOffset: 2, latitude: 48.8566, longitude: 2.3522, name: 'Person B' },
};
const res = await fetch('https://api.astroway.info/v1/synastry', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
    'X-Api-Key': process.env.ASTROWAY_API_KEY!,
  },
  body: JSON.stringify(body),
});
const { data: result } = await res.json();
console.log(result.compatibility);
console.log(result.crossAspects.length);

Python

import os, requests

body = {
    'chart1': {'date': '1990-07-14', 'time': '14:30:00', 'timezoneOffset': 3, 'latitude': 50.4501, 'longitude': 30.5234, 'name': 'Person A'},
    'chart2': {'date': '1992-03-22', 'time': '09:15:00', 'timezoneOffset': 2, 'latitude': 48.8566, 'longitude': 2.3522, 'name': 'Person B'},
}
r = requests.post(
    'https://api.astroway.info/v1/synastry',
    headers={'X-Api-Key': os.environ['ASTROWAY_API_KEY'], 'Content-Type': 'application/json'},
    json=body,
)
result = r.json()['data']
print(result['compatibility'])

PHP

<?php
use GuzzleHttp\Client;

$aw = new Client(['base_uri' => 'https://api.astroway.info/v1/']);
$r = $aw->post('synastry', [
    'headers' => ['X-Api-Key' => getenv('ASTROWAY_API_KEY')],
    'json' => [
        'chart1' => ['date' => '1990-07-14', 'time' => '14:30:00', 'timezoneOffset' => 3, 'latitude' => 50.4501, 'longitude' => 30.5234, 'name' => 'Person A'],
        'chart2' => ['date' => '1992-03-22', 'time' => '09:15:00', 'timezoneOffset' => 2, 'latitude' => 48.8566, 'longitude' => 2.3522, 'name' => 'Person B'],
    ],
]);
$result = json_decode($r->getBody(), true)['data'];
print_r($result['compatibility']);

Example response

{
  "chart1": {
    "input": { "date": "1990-07-14", "name": "Person A" },
    "planets": [ ... ],
    "houses": { ... },
    "aspects": [ ... ]
  },
  "chart2": {
    "input": { "date": "1992-03-22", "name": "Person B" },
    "planets": [ ... ],
    "houses": { ... },
    "aspects": [ ... ]
  },
  "crossAspects": [
    {
      "planet1": "Sun",
      "planet2": "Venus",
      "chart1Planet": "Sun",
      "chart2Planet": "Venus",
      "type": "trine",
      "orb": 2.14,
      "applying": false
    },
    {
      "planet1": "Moon",
      "planet2": "Mars",
      "chart1Planet": "Moon",
      "chart2Planet": "Mars",
      "type": "square",
      "orb": 0.87,
      "applying": true
    }
  ],
  "compatibility": {
    "score": 51,
    "label": "mixed",
    "harmony": 15.8,
    "tension": 16.8,
    "top": [
      { "aspect": { "planet1": "Venus", "planet2": "Moon", "type": { "name": "Square", "angle": 90 } }, "strength": 2.09, "sign": -1 }
    ]
  }
}

Note

chart1 and chart2 are full natal charts (same fields as /v1/chart). crossAspects are aspects between planets of the two charts. compatibility.score is 0 to 100.

compatibility field

Field	Type	Description
score	number	Overall 0–100 score
label	string	harmonious, balanced, mixed, challenging
harmony	number	Weighted sum of the aspects that scored as harmony
tension	number	Weighted sum of the aspects that scored as tension
top	array	The five heaviest aspects behind the score, each with its strength and its sign (1 harmony, -1 tension)

Related endpoints

Endpoint	Credits	What it adds
/v1/composite	50	Composite chart (midpoints)
/v1/davison	50	Davison chart (mean date)
/v1/coalescent	50	Coalescent chart
/v1/group-synastry	100	Compatibility matrix for 2–10 people
/v1/human-design/compatibility	100	HD compatibility

Next

• Natal chart: basic request
• Transits: transit overlay
• Human Design: full HD chart
• API reference: all 760 endpoints