Photometry & distance · θ = 2 arctan(D / 2d)
Angular Diameter
How large an object of known size appears at a given distance. The Moon and the Sun span almost exactly the same half-degree from Earth — the coincidence that makes total solar eclipses possible.
Angular diameter1864.5arcsec
Formula: θ = 2 arctan(D / 2d)
Worked example
With the default inputs, angular diameter evaluates to 1864.5 arcsec — The Moon → ~1865″ (0.52°). The validator recomputes this against the known value on every build, so the formula is checked, not asserted.
Highlights
- ›The Moon: ~0.52°
The physics behind it
Knowledge connections
- Associated withParallax Distance
Sources
The primary and reference sources this topic draws on.
- NASANational Aeronautics and Space Administration
Mission data, planetary science, space telescopes, and public-domain imagery.
Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.