Lunar Phase Illumination Percent
Distant-Sun spherical lunar illumination proxy from unoriented 0..180 elongation; phase age/waxing direction not determined. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Description
Lunar elongation and illuminated fraction are connected under distant-Sun geometry.
Lunar elongation and illuminated fraction are connected under distant-Sun geometry.1
Illumination percentage is distinct from lunar age, angular size and local visibility. Use Lunar Phase Illumination Percent to evaluate the supplied inputs under the model explained below.
When to use Lunar Phase Illumination Percent
Use Lunar Phase Illumination Percent to evaluate the supplied inputs under the model explained below. Establish the units, measurement scope and model assumptions before entering values.
How to use Lunar Phase Illumination Percent and understand its results
- Establish the units, measurement scope and model assumptions before entering values.
- Enter Observed sun moon elongation degrees using the field table and validation rules below, then run the tool.
- Read Distant sun lunar illumination percent; 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 |
|---|---|---|---|
| observedSunMoonElongationDegrees | Observed sun moon elongation degrees | number | Required; constraints below |
Enter observed Sun–Moon elongation from 0 to 180 degrees. Return 50×(1−cos(elongation)) as percent illuminated under distant-Sun geometry. Endpoints give 0 and 100; 90° gives approximately 50. No lunar age or local phase ephemeris is computed.
illuminationPercent=50×(1−cos(elongationDegrees)) Use the field order, units and branch conditions described above.
| Output field | Meaning | Value type |
|---|---|---|
| distantSunLunarIlluminationPercent | Distant sun lunar illumination percent | number |
{
"input": {
"observedSunMoonElongationDegrees": 90
},
"output": {
"distantSunLunarIlluminationPercent": 49.99999999999999
}
}Limitations and assumptions
Illumination percentage is distinct from lunar age, angular size and local visibility. 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 Supermoon Size Increase Percent Check for a related task: An apparent lunar size increase requires an explicit comparison observation.
Use Moon Age Days From Elongation for a related task: Elongation can be turned into an age within a uniform synodic-cycle model.
References
-
Lunar Phase Illumination Percent — tool.io
Similar or alternative tools
- Supermoon Size Increase Percent Check
An apparent lunar size increase requires an explicit comparison observation.
- Moon Age Days From Elongation
Elongation can be turned into an age within a uniform synodic-cycle model.