# Synastry score and cross-aspects (public, no key)

`POST https://api.astroway.info/v1/public/synastry`

Compatibility score and the planet-to-planet aspect grid for two birth charts, served anonymously. Aspects come back sorted by orb, tightest first, so taking the first six gives the six an embed would show. `applying` is true when the aspect is still closing. What stays behind a key: the per-aspect interpretations, the house overlay, composite and Davison charts, and the two natal charts themselves, all of which the authed POST /synastry returns. Either partner may set `timeUnknown: true`; cross-aspects survive an unknown time because they are planet to planet. **This call costs 3 units** of the public rate-limit bucket rather than 1, because it computes two charts and the full matrix: 10 an hour on an undeclared address, 100 per declared site, 200 per address. The response carries `X-RateLimit-Cost: 3`.

Group: Public. Auth: none, this endpoint answers without a key.

## Parameters

| Name | In | Required | Type | Description |
|---|---|---|---|---|
| `fields` | query | no | string | Comma-separated dotted paths, relative to `data`, to keep in the response. A path is applied to every element of an array, so `planets.name` means the name of each planet. Paths that match nothing come back in `_fields_unmatched`; a list where nothing matches at all is a 400, because an empty object would be a confident wrong answer. |
| `precision` | query | no | integer | Round every non-integer number in the response to this many decimal places. Integers are left alone, because an id is not a measurement. Ecliptic longitudes ship with fourteen decimals by default; 2 is about a tenth of an arcminute. |

## Request body

| Field | Type | Required | Description |
|---|---|---|---|
| `chart1` | object | yes | Birth data where the clock time may be unknown. Either pass time (HH:mm:ss), or set timeUnknown: true and omit it. In the second case the response carries planets and aspects but no houses, angles or sect. |
| `chart1.date` | string | yes |  |
| `chart1.time` | string | no |  |
| `chart1.timezoneOffset` | number | no | Hours from UTC at the given moment, not minutes. Fractional zones are hours too: 5.5 for India, 5.75 for Nepal, -3.5 for Newfoundland. Defaults to 0, meaning UTC. Ignored when timezone is sent. |
| `chart1.timezone` | string | no | IANA zone name such as Europe/Kyiv, or auto to look the zone up from latitude and longitude. The server takes the offset that zone kept at this local date and time, summer time included, and uses it in place of timezoneOffset. A clock time that happened twice takes the first occurrence; one skipped when clocks went forward takes the offset from before the change. Abbreviations such as EST are refused. Before 1970 the tz database is not reliable for every place, so send timezoneOffset when the local clock is known. |
| `chart1.latitude` | number | yes |  |
| `chart1.longitude` | number | yes |  |
| `chart1.houseSystem` | "P" \| "K" \| "R" \| "C" \| "E" \| "W" \| "B" \| "M" \| … | no |  |
| `chart1.name` | string | no |  |
| `chart1.city` | string | no |  |
| `chart1.zodiacType` | "tropical" \| "sidereal" | no |  |
| `chart1.ayanamsaId` | number | no |  |
| `chart1.ayanamsa` | "fagan-bradley" \| "lahiri" \| "de-luce" \| "raman" \| "krishnamurti" \| "kp" \| "yukteshwar" \| "jn-bhasin" \| … | no | Sidereal school by name. Lahiri when omitted. Equivalent to ayanamsaId; send either. |
| `chart1.cosmogram` | boolean | no |  |
| `chart1.timeUnknown` | boolean | no |  |
| `chart2` | object | yes | Birth data where the clock time may be unknown. Either pass time (HH:mm:ss), or set timeUnknown: true and omit it. In the second case the response carries planets and aspects but no houses, angles or sect. |
| `chart2.date` | string | yes |  |
| `chart2.time` | string | no |  |
| `chart2.timezoneOffset` | number | no | Hours from UTC at the given moment, not minutes. Fractional zones are hours too: 5.5 for India, 5.75 for Nepal, -3.5 for Newfoundland. Defaults to 0, meaning UTC. Ignored when timezone is sent. |
| `chart2.timezone` | string | no | IANA zone name such as Europe/Kyiv, or auto to look the zone up from latitude and longitude. The server takes the offset that zone kept at this local date and time, summer time included, and uses it in place of timezoneOffset. A clock time that happened twice takes the first occurrence; one skipped when clocks went forward takes the offset from before the change. Abbreviations such as EST are refused. Before 1970 the tz database is not reliable for every place, so send timezoneOffset when the local clock is known. |
| `chart2.latitude` | number | yes |  |
| `chart2.longitude` | number | yes |  |
| `chart2.houseSystem` | "P" \| "K" \| "R" \| "C" \| "E" \| "W" \| "B" \| "M" \| … | no |  |
| `chart2.name` | string | no |  |
| `chart2.city` | string | no |  |
| `chart2.zodiacType` | "tropical" \| "sidereal" | no |  |
| `chart2.ayanamsaId` | number | no |  |
| `chart2.ayanamsa` | "fagan-bradley" \| "lahiri" \| "de-luce" \| "raman" \| "krishnamurti" \| "kp" \| "yukteshwar" \| "jn-bhasin" \| … | no | Sidereal school by name. Lahiri when omitted. Equivalent to ayanamsaId; send either. |
| `chart2.cosmogram` | boolean | no |  |
| `chart2.timeUnknown` | boolean | no |  |

```json
{
  "chart1": {
    "date": "1990-07-14",
    "time": "14:30:00",
    "timezoneOffset": 3,
    "latitude": 50.45,
    "longitude": 30.52
  },
  "chart2": {
    "date": "1992-03-22",
    "time": "09:15:00",
    "timezoneOffset": 2,
    "latitude": 48.85,
    "longitude": 2.35
  }
}
```

## Responses

| Status | Meaning |
|---|---|
| 200 | OK |
| 400 | Invalid input |

### Success fields, under `data`

| Field | Type | Required | Description |
|---|---|---|---|
| `score` | number | no |  |
| `label` | string | no |  |
| `aspects` | object[] | no |  |
| `count` | number | no |  |

## Example

```bash
curl -X POST 'https://api.astroway.info/v1/public/synastry' \
  -H 'Content-Type: application/json' \
  -d '{"chart1":{"date":"1990-07-14","time":"14:30:00","timezoneOffset":3,"latitude":50.45,"longitude":30.52},"chart2":{"date":"1992-03-22","time":"09:15:00","timezoneOffset":2,"latitude":48.85,"longitude":2.35}}'
```

---

Rendered from https://api.astroway.info/v1/openapi.json. HTML page: https://api.astroway.info/docs/api/operations/publicsynastry/