Local Sidereal Time from GST Longitude Calculator
LST from independently known GST and east-positive longitude, no date/UT/GMST or geodesy calculation. Caller independently establishes frames, units, epoch, covariance and instrument context; not an identity, association or astrometric quality certification.
Description
Local sidereal time depends on Greenwich sidereal time and east-positive longitude.
Local sidereal time depends on Greenwich sidereal time and east-positive longitude.1
A supplied Greenwich value is distinct from computing Earth's rotation from a civil timestamp. Use Local Sidereal Time from GST Longitude Calculator to evaluate the supplied inputs under the model explained below.
When to use Local Sidereal Time from GST Longitude Calculator
Use Local Sidereal Time from GST Longitude Calculator to evaluate the supplied inputs under the model explained below. Establish the units, measurement scope and model assumptions before entering values.
How to use Local Sidereal Time from GST Longitude Calculator and understand its results
- Establish the units, measurement scope and model assumptions before entering values.
- Enter Greenwich sidereal hours, East longitude degrees using the field table and validation rules below, then run the tool.
- Read Local sidereal hours; interpret the units, signs, ordering and unknown-value placeholders described below.
- Correct reported input errors and rerun. Apply successful results according to their specific meanings and check the assumptions before using them in a decision.
| Input field | Meaning | Value type | Requirement |
|---|---|---|---|
| greenwichSiderealHours | Greenwich sidereal hours | number | Required; constraints below |
| eastLongitudeDegrees | East longitude degrees | number | Required; constraints below |
Enter finite Greenwich sidereal hours and east-positive longitude from −180 to 180 degrees. Add longitude/15 and wrap to [0,24) hours. No Greenwich-time computation, nutation model or civil-time conversion occurs.
localSiderealHours=wrap24(GreenwichSiderealHours+eastLongitude/15) Use the field order, units and branch conditions described above.
| Output field | Meaning | Value type |
|---|---|---|
| localSiderealHours | Local sidereal hours | number |
{
"input": {
"greenwichSiderealHours": 23,
"eastLongitudeDegrees": 30
},
"output": {
"localSiderealHours": 1
}
}Limitations and assumptions
A supplied Greenwich value is distinct from computing Earth's rotation from a civil timestamp. Apply the exact scope and assumptions explained above.
All listed fields require explicit values. Unexpected fields, incorrect types, nonfinite numbers and sparse arrays fail validation. Domain-specific bounds, alignments and supported tokens are explained above; extremely large inputs or outputs can also be rejected. Input errors differ from successful false results, empty match lists and unknown-evidence placeholders.
Alternative or Complementary methods
Use Transit Time Upper Culmination Hour Finder for a related task: Upper culmination occurs when local sidereal time matches right ascension.
Use Hour Angle from Right Ascension and LST Solver for a related task: Hour angle measures local sidereal time relative to right ascension.
References
Similar or alternative tools
- Transit Time Upper Culmination Hour Finder
Upper culmination occurs when local sidereal time matches right ascension.
- Hour Angle from Right Ascension and LST Solver
Hour angle measures local sidereal time relative to right ascension.