Photometry & distance · cos θ = sin δ₁ sin δ₂ + cos δ₁ cos δ₂ cos(α₁ − α₂)
Angular Separation
The angle on the sky between two positions given by their right ascension and declination — the great-circle distance between two points on the celestial sphere.
Angular separation10°
Formula: cos θ = sin δ₁ sin δ₂ + cos δ₁ cos δ₂ cos(α₁ − α₂)
Worked example
With the default inputs, angular separation evaluates to 10 ° — (0,0) & (0,+10°) → 10°. The validator recomputes this against the known value on every build, so the formula is checked, not asserted.
Highlights
- ›Great-circle distance on the sky
The physics behind it
Knowledge connections
- Associated withThe International Celestial Reference System
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.