# Star-planet parans (Brady)

`POST https://api.astroway.info/v1/parans/star`

Latitudes where a fixed star and a planet are angular at the same moment, which is how Brady tabulates a paran: not a place, a latitude. Twelve event pairs per star and planet (rise, set, culminate, anticulminate, minus meridian against meridian, which is a shared right ascension rather than a paran). Each row carries the houses of the technique in plain form: which body does what, the latitude, and the meridian where it happens at this chart moment. Solved on hour angles rather than by intersecting map polylines, so the latitude is exact rather than quantised to the polyline step. `horizon` selects the geometric horizon (default) or the apparent one at -34 arcmin, measured at about two degrees of paran latitude at mid-latitudes.

Group: Astro-Geography. Auth: `X-Api-Key` header. Operation ID: `parans_star`.

## 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 |
|---|---|---|---|
| `date` | string | yes |  |
| `time` | string | yes |  |
| `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. |
| `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. |
| `latitude` | number | yes |  |
| `longitude` | number | yes |  |
| `houseSystem` | "P" \| "K" \| "R" \| "C" \| "E" \| "W" \| "B" \| "M" \| … | no |  |
| `name` | string | no |  |
| `city` | string | no |  |
| `zodiacType` | "tropical" \| "sidereal" | no |  |
| `ayanamsaId` | number | no |  |
| `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. |
| `cosmogram` | boolean | no |  |
| `stars` | string[] | no | Star names from the Swiss Ephemeris catalogue. Default: the 36-star astrological set. |
| `planets` | integer[] | no | Swiss Ephemeris planet ids. Default: 0-9, Sun through Pluto. |
| `latitudeLimit` | number | no | Search range either side of the equator, degrees. Default 60, which is the range Brady tabulates. |
| `horizon` | "geometric" \| "apparent" | no | Which horizon counts as rising. `geometric` (default) is altitude 0, the semi-diurnal arc as written in Meeus. `apparent` puts it at -34 arcmin, where refraction lifts a body into view first. Worth about two degrees of paran latitude at mid-latitudes, and refraction also breaks the equator mirror that the geometric horizon has, so it is a choice rather than a detail. |

```json
{
  "date": "1990-05-15",
  "time": "15:30:00",
  "timezone": "Europe/Kyiv",
  "stars": [
    "Regulus",
    "Sirius"
  ],
  "planets": [
    0,
    4
  ],
  "latitudeLimit": 60,
  "horizon": "geometric"
}
```

## Responses

| Status | Meaning |
|---|---|
| 200 | Successful calculation |
| 400 | Validation error |
| 401 | Missing or invalid API key |

### Success fields, under `data`

| Field | Type | Required | Description |
|---|---|---|---|
| `type` | string | no |  |
| `julianDay` | number | no |  |
| `gmst` | number | no |  |
| `obliquity` | number | no |  |
| `latitudeLimit` | number | no |  |
| `horizon` | string | no |  |
| `count` | number | no |  |
| `stars` | object[] | no |  |
| `requestedStarsNotFound` | object[] | no |  |
| `starsWithNoParans` | object[] | no |  |
| `parans` | object[] | no |  |
| `note` | string | no |  |

## Example

```bash
curl -X POST https://api.astroway.info/v1/parans/star \
  -H "X-Api-Key: aw_live_..." \
  -H "Content-Type: application/json" \
  -d '{ "date": "1990-05-15", "time": "15:30:00", "timezone": "Europe/Kyiv", "stars": [ "Regulus", "Sirius" ], "planets": [ 0, 4 ], "latitudeLimit": 60, "horizon": "geometric" }'
```

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