Sidereal time API

Returns Greenwich mean sidereal time (GMST) and, with a longitude, local mean sidereal time (LMST) in degrees, hours, and HMS for a UTC instant (IAU 1982). Answers 'What is the sidereal time now?', 'Local sidereal time at this longitude?'.

Price$0.06per request

MethodPOST

Route/v1/space/sidereal-time

StatusLive

MIME typeapplication/json

Rate limit120/minute

Cache0s public

spaceastronomysidereal-timegmstlmsthour-anglepositional-astronomytelescope

API URLhttps://x402.hexl.dev/v1/space/sidereal-time

Integration docs

Example request

{
  "date": "2024-06-21T18:00:00Z",
  "longitude": -75
}

Example response

{
  "date": "2024-06-21T18:00:00.000Z",
  "julianDate": 2460483.25,
  "gmstDeg": 180.423213,
  "gmstHours": 12.02821422,
  "longitude": -75,
  "lmstDeg": 105.423213,
  "lmstHours": 7.02821422,
  "lmstHMS": "07:01:42",
  "interpretation": "GMST is 12.0282 h; local sidereal time 7.0282 h."
}

Input schema

{
  "type": "object",
  "required": [
    "date"
  ],
  "properties": {
    "date": {
      "type": "string",
      "description": "ISO 8601 date/time (UTC)",
      "examples": [
        "2024-06-21T18:00:00Z"
      ]
    },
    "longitude": {
      "type": "number",
      "description": "Observer longitude in degrees, east positive",
      "examples": [
        -75
      ]
    }
  }
}

Output schema

{
  "type": "object",
  "additionalProperties": true
}