Angular Resolution Calculator

Your details

Choose whether to calculate resolution or the aperture needed to achieve a target resolution.
The Rayleigh criterion is the standard; Dawes is used for visual double-star work; Sparrow represents the absolute diffraction limit.
The clear opening of the lens, mirror, or pupil. Larger apertures give finer angular resolution.
mm
The wavelength of light in nanometres. Visible light spans ~380-700 nm; green (~550 nm) is commonly used as the mid-band reference.
nm
Optional. Used to compute the linear (physical) separation at the object that corresponds to the angular resolution. Leave blank or 0 to skip.
m
Angular resolutionVery good (below 1 arcsec)
0.692arcsec

Minimum resolvable angular separation between two point sources

Angular resolution0.0115arcmin
Angular resolution0.000192deg
Angular resolution0.00000336rad
Linear resolution at distance0.0034m
Airy disk radius0.692arcsec
0.692 arcsec
Excellent<0.1Very good0.1-1Good1-10Moderate10-60Coarse60+

Diffraction limit: 0.6920 arcsec under the Rayleigh criterion.

  • Resolution below 1 arcsec approaches the ground-based seeing limit. Large-aperture telescopes with adaptive optics can reach this.
  • At 1000 m, the minimum resolvable feature size is 0.0034 m (0.34 cm).
  • Atmospheric seeing (typically 1-3 arcsec at ground level) often limits ground-based telescopes before the diffraction limit is reached.

Next stepFor real telescopes, compare this theoretical limit to the typical atmospheric seeing at your site (usually 1-3 arcsec) to see whether aperture or atmosphere is the binding constraint.

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