Hour Angle from Right Ascension and LST Solver
Signed local hour angle LST−RA wrapped−12..12 hours, consistent equinox/frame/time caller supplied. Caller independently establishes frames, units, epoch, covariance and instrument context; not an identity, association or astrometric quality certification.
Description
Hour angle measures local sidereal time relative to right ascension.
Hour angle measures local sidereal time relative to right ascension.1
A signed wrap convention must be specified at the half-day boundary. Use Hour Angle from Right Ascension and LST Solver to evaluate the supplied inputs under the model explained below.
When to use Hour Angle from Right Ascension and LST Solver
Use Hour Angle from Right Ascension and LST Solver to evaluate the supplied inputs under the model explained below. Establish the units, measurement scope and model assumptions before entering values.
How to use Hour Angle from Right Ascension and LST Solver and understand its results
- Establish the units, measurement scope and model assumptions before entering values.
- Enter Local sidereal hours, Right ascension hours using the field table and validation rules below, then run the tool.
- Read Signed hour angle 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 |
|---|---|---|---|
| localSiderealHours | Local sidereal hours | number | Required; constraints below |
| rightAscensionHours | Right ascension hours | number | Required; constraints below |
Enter finite local sidereal and right-ascension hours. Return wrap24(LST−RA+12)−12 in [−12,12). A positive 12-hour difference maps to −12. No observation timestamp, refraction or sky-coordinate calculation is supplied.
signedHourAngleHours=wrap24(LST−RA+12)−12 Use the field order, units and branch conditions described above.
| Output field | Meaning | Value type |
|---|---|---|
| signedHourAngleHours | Signed hour angle hours | number |
{
"input": {
"localSiderealHours": 1,
"rightAscensionHours": 23
},
"output": {
"signedHourAngleHours": 2
}
}Limitations and assumptions
A signed wrap convention must be specified at the half-day boundary. 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 Local Sidereal Time from GST Longitude Calculator for a related task: Local sidereal time depends on Greenwich sidereal time and east-positive longitude.
References
Similar or alternative tools
- Transit Time Upper Culmination Hour Finder
Upper culmination occurs when local sidereal time matches right ascension.
- Local Sidereal Time from GST Longitude Calculator
Local sidereal time depends on Greenwich sidereal time and east-positive longitude.