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.

RA 1 (°)Dec 1 (°)RA 2 (°)Dec 2 (°)

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 International Celestial Reference System

Knowledge connections

Associated withThe International Celestial Reference System

Sources

Facts on this topic will be cited from these primary and reference sources.

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.

Loading…

Angular Separation

Worked example

Highlights

The physics behind it

Knowledge connections

Sources

Angular Separation

Worked example

Highlights

The physics behind it

Knowledge connections

Sources