Civil Twilight End Hour Angle
Declaredcivil twilightgeometricSun−6°hourangle,notclocktimestamp/ephemeris/daylength. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Description
Civil twilight conventionally uses the solar center six degrees below a geometric horizon.
Civil twilight conventionally uses the solar center six degrees below a geometric horizon.1
This tool calculates the boundary hour angle from supplied latitude and declination; it returns an angle and crossing condition rather than a local clock time.
When to use Civil Twilight End Hour Angle
Use this tool to apply the stated civil twilight end hour angle operation with an explicit input and unit basis.
How to use Civil Twilight End Hour Angle and how it works
- Establish the measurement basis and units described above.
- Enter actualLatitudeDegrees, callerIndependentSolarDeclinationDegrees and run the tool.
- Read result.civilTwilightBoundaryHourAngleDegrees, result.condition using the output meanings below.
- If input is rejected, correct the stated type, range, ordering or alignment issue and rerun; review successful results under the declared convention.
| Input field | Meaning | Value type | Requirement |
|---|---|---|---|
| actualLatitudeDegrees | Latitude Degrees. Units, ordering and applicable branch are specified in the algorithm. | number | required; finite; further conditions in the algorithm |
| callerIndependentSolarDeclinationDegrees | Solar Declination Degrees. Units, ordering and applicable branch are specified in the algorithm. | number | required; finite; further conditions in the algorithm |
Use the shared geometric hour-angle equation at altitude −6 degrees. Reject polar latitude or declination; return H=0 for never-reaches-altitude, H=180 for always-above-altitude and acos(x) otherwise. No date, timezone, refraction or evening clock conversion is performed.
x = (sin(−6°)−sinφ sinδ)/(cosφ cosδ); H = acos(x) on crossing branch Apply the declared units, ordering and branch conditions.
| Output field | Meaning | Value type |
|---|---|---|
| result | Object containing the declared output fields. | object |
| result.civilTwilightBoundaryHourAngleDegrees | Nonnegative boundary hour angle in degrees, with a noncrossing sentinel described by condition. | number |
| result.condition | Branch label describing geometric crossing or noncrossing, as explained in the algorithm. | string |
{
"input": {
"actualLatitudeDegrees": 0,
"callerIndependentSolarDeclinationDegrees": 0
},
"output": {
"result": {
"civilTwilightBoundaryHourAngleDegrees": 96,
"condition": "crossing"
}
}
}Limitations and assumptions
The output applies the declared operation to the values you supply. Establish the measurement basis, units, coefficients and any caller-selected rules before interpreting it. The tool does not independently collect or verify observations or decide whether a model or reference applies.
Supply explicit required fields with the documented types and dense aligned arrays. Unknown fields, wrong types and nonfinite numbers are rejected. Branch-specific constraints are explained above. A returned boolean, signed difference or tied result follows the stated convention; an input error instead means the required input contract was not satisfied. Very large inputs or outputs may be rejected by shared resource limits.
Alternative or Complementary methods
For a related operation, use Daylight Duration Latitude Calculator. Geometric daylight uses the solar center crossing an ideal zero-altitude horizon.
For a related operation, use Rise/Set Hour Angle Formula. Rise and set geometry can be formulated as crossings of a caller-selected altitude.
References
-
Civil Twilight End Hour Angle — tool.io
Similar or alternative tools
- Daylight Duration Latitude Calculator
Geometric daylight uses the solar center crossing an ideal zero-altitude horizon.
- Rise/Set Hour Angle Formula
Rise and set geometry can be formulated as crossings of a caller-selected altitude.