Time Conversion

Sidereal Time (LAST & GMST)

Compute Local Apparent Sidereal Time (LAST) and Greenwich Mean Sidereal Time (GMST).

get/time/sidereal

Request

  • Base URL: https://api.openephemeris.com
  • URL: https://api.openephemeris.com/time/sidereal
  • Auth: one of:
    • HTTP bearer
    • API key in header X-OpenEphemeris-API-Key
    • API key in header X-API-Key
    • API key in header X-Service-Key

Query parameters

datestring required

Date (YYYY-MM-DD) or Julian Day (jd:2451545.0)

Example:2026-03-15
longitudenumber

Observer longitude (positive East)

Headers

authorizationstring nullable
X-API-Keystring nullable
X-OpenEphemeris-API-Keystring nullable
apikeystring nullable

Response

Successful Response

equation_of_equinoxesnumber required

The nutation correction in hours

gmstnumber required

Greenwich Mean Sidereal Time in hours

informationobject required

Metadata about the calculation engine

lastnumber required

Local Apparent Sidereal Time in hours

longitude_usednumber required

The observer longitude used for LAST

Changes

No recorded changes to this operation across all 1 revision of this API.