Moon Apparent Size Perigee/Apogee Arcmin
ExactSPHERICALlimb2asin(R/d)Moonangularsizeactualperigee/apogeedistances,not disk2atanor observedpercentageincrease. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Description
A spherical Moon’s apparent limb diameter grows when its center is closer to the observer.
A spherical Moon’s apparent limb diameter grows when its center is closer to the observer.1
This calculator uses a supplied lunar radius and two center distances in kilometers to compare perigee and apogee angles.
When to use Moon Apparent Size Perigee/Apogee Arcmin
Use this tool to apply the stated moon apparent size perigee/apogee arcmin operation with an explicit input and unit basis.
How to use Moon Apparent Size Perigee/Apogee Arcmin and how it works
- Establish the measurement basis and units described above.
- Enter actualLunarRadiusKm, callerActualPerigeeDistanceKm, callerActualApogeeDistanceKm and run the tool.
- Read result.perigeeAngularDiameterArcminutes, result.apogeeAngularDiameterArcminutes 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 |
|---|---|---|---|
| actualLunarRadiusKm | Lunar Radius Km. Units, ordering and applicable branch are specified in the algorithm. | number | required; finite; strictly positive; further conditions in the algorithm |
| callerActualPerigeeDistanceKm | Perigee Distance Km. Units, ordering and applicable branch are specified in the algorithm. | number | required; finite; strictly positive; further conditions in the algorithm |
| callerActualApogeeDistanceKm | Apogee Distance Km. Units, ordering and applicable branch are specified in the algorithm. | number | required; finite; strictly positive; further conditions in the algorithm |
Require positive radius, perigee distance greater than the radius and apogee distance at least perigee distance. Apply twice arcsin(radius/distance) at each distance and convert radians to arcminutes; no orbital distances are fetched.
angularDiameterArcmin = 2asin(radius/distance) × 180/π × 60 Apply the declared units, ordering and branch conditions.
| Output field | Meaning | Value type |
|---|---|---|
| result | Object containing the declared output fields. | object |
| result.perigeeAngularDiameterArcminutes | Spherical-limb angular diameter at the supplied closer distance, in arcminutes. | number |
| result.apogeeAngularDiameterArcminutes | Spherical-limb angular diameter at the supplied farther distance, in arcminutes. | number |
{
"input": {
"actualLunarRadiusKm": 1,
"callerActualPerigeeDistanceKm": 2,
"callerActualApogeeDistanceKm": 4
},
"output": {
"result": {
"perigeeAngularDiameterArcminutes": 3600.0000000000005,
"apogeeAngularDiameterArcminutes": 1737.3014623115907
}
}
}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 Moon Phase Approximation Calculator. A mean synodic lunar cycle is a simple repeating phase clock.
For a related operation, use Golden Hour Duration By Latitude Lookup. Golden-hour definitions vary by photographic convention.
References
-
Moon Apparent Size Perigee/Apogee Arcmin — tool.io
Similar or alternative tools
- Moon Phase Approximation Calculator
A mean synodic lunar cycle is a simple repeating phase clock.
- Golden Hour Duration By Latitude Lookup
Golden-hour definitions vary by photographic convention.