Angular Resolution Calculator

What Is Angular Resolution?

Angular resolution is the smallest angular separation at which an optical instrument can distinguish two point sources. A smaller angle means finer detail. Telescopes, microscopes, cameras, and even the human eye are all limited by diffraction and described with the Rayleigh criterion.

Rayleigh Criterion Formula

\(\theta\) is the angular resolution in radians, \(\lambda\) is the wavelength of light, and \(D\) is the aperture diameter. For green light at \(\lambda = 550\,\text{nm}\) and a \(100\,\text{mm}\) aperture:

Converting Angular Units

Radians convert to degrees with \(\theta_{\deg} = \theta_{\text{rad}} \times 180/\pi\). One degree equals \(3600\) arcseconds, so \(\theta_{\text{arcsec}} = \theta_{\text{rad}} \times 206265\). Astronomers often quote resolution in arcseconds; photographers may prefer degrees or arcminutes.