Angular Size From Diameter and Distance
Exactplanartransversediskatanangulardiameter,degrees,diametercenterlineplaneperpendicularLOS;NOTsphericallimb2asin(R/d)orsmallangle. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Description
A planar disk’s angular diameter follows exact tangent geometry at its center distance.
A planar disk’s angular diameter follows exact tangent geometry at its center distance.1
This calculator returns degrees from a transverse diameter and distance in matching units; it is not the spherical-limb arcsine formula.
When to use Angular Size From Diameter and Distance
Use this tool to apply the stated angular size from diameter and distance operation with an explicit input and unit basis.
How to use Angular Size From Diameter and Distance and how it works
- Establish the measurement basis and units described above.
- Enter actualTransverseDiameter, actualCenterDistance and run the tool.
- Read result.value 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 |
|---|---|---|---|
| actualTransverseDiameter | Transverse Diameter. Units, ordering and applicable branch are specified in the algorithm. | number | required; finite; nonnegative; further conditions in the algorithm |
| actualCenterDistance | Center Distance. Units, ordering and applicable branch are specified in the algorithm. | number | required; finite; strictly positive; further conditions in the algorithm |
Require nonnegative diameter and positive distance. Evaluate 2atan(diameter/(2distance)) and convert radians to degrees, without imposing a small-angle approximation.
angularDiameterDegrees = 2atan(diameter/(2distance)) × 180/π Apply the declared units, ordering and branch conditions.
| Output field | Meaning | Value type |
|---|---|---|
| result | Object containing the declared output fields. | object |
| result.value | Planar-disk angular diameter in degrees. | number |
{
"input": {
"actualTransverseDiameter": 2,
"actualCenterDistance": 1
},
"output": {
"result": {
"value": 90
}
}
}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 Star Trail Length Pixels Per Minute. A stationary camera records star motion caused by Earth’s sidereal rotation.
For a related operation, use Small Angle Formula Arcseconds Calculator. The small-angle formula relates a transverse physical size to an angular size when the size-to-distance ratio is small.
References
-
Angular Size From Diameter and Distance — tool.io
Similar or alternative tools
- Star Trail Length Pixels Per Minute
A stationary camera records star motion caused by Earth’s sidereal rotation.
- Small Angle Formula Arcseconds Calculator
The small-angle formula relates a transverse physical size to an angular size when the size-to-distance ratio is small.