Blue Hour Duration By Latitude Lookup
Explicittoy eveningblue−6…−4°Sunwindowgeometricdurationfromactualindependentdeclination/latitude,not universalaestheticdefinitionor live ephemeris. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Description
Blue-hour definitions depend on the chosen solar-altitude interval.
Blue-hour definitions depend on the chosen solar-altitude interval.1
This tool uses a declared evening window from −4 to −6 degrees and caller-supplied declination instead of providing a dated sunrise or sunset lookup.
When to use Blue Hour Duration By Latitude Lookup
Use this tool to apply the stated blue hour duration by latitude lookup operation with an explicit input and unit basis.
How to use Blue Hour Duration By Latitude Lookup and how it works
- Establish the measurement basis and units described above.
- Enter actualLatitudeDegrees, callerIndependentSolarDeclinationDegrees and run the tool.
- Read result.declaredEveningWindowMinutes, 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 |
Calculate geometric hour-angle boundaries at −4 and −6 degrees. If both cross, return four times the evening angle difference in minutes; otherwise return zero with the noncrossing condition. Exact polar latitude and declination are rejected.
eveningWindowMinutes = 4 × (H at −6° − H at −4°), only when both boundaries cross Apply the declared units, ordering and branch conditions.
| Output field | Meaning | Value type |
|---|---|---|
| result | Object containing the declared output fields. | object |
| result.declaredEveningWindowMinutes | Ideal elapsed minutes when both boundaries cross; zero is a sentinel otherwise. | number |
| result.condition | Branch label describing geometric crossing or noncrossing, as explained in the algorithm. | string |
{
"input": {
"actualLatitudeDegrees": 0,
"callerIndependentSolarDeclinationDegrees": 0
},
"output": {
"result": {
"declaredEveningWindowMinutes": 8,
"condition": "both-boundaries-cross"
}
}
}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 Golden Hour Duration By Latitude Lookup. Golden-hour definitions vary by photographic convention.
For a related operation, use Civil Twilight End Hour Angle. Civil twilight conventionally uses the solar center six degrees below a geometric horizon.
References
-
Blue Hour Duration By Latitude Lookup — tool.io
Similar or alternative tools
- Golden Hour Duration By Latitude Lookup
Golden-hour definitions vary by photographic convention.
- Civil Twilight End Hour Angle
Civil twilight conventionally uses the solar center six degrees below a geometric horizon.