Rayleigh Criterion (Resolution)
Find the smallest angle and separation a telescope, camera lens or eye can resolve from its aperture and wavelength, free online.
About this calculator
The Rayleigh criterion for a circular aperture is ฮธ = 1.22 ฮป รท D radians. Two point sources closer than this angle blur into one. The smallest resolvable separation at distance L is about Lยทฮธ. The human pupil (โ 4 mm, 550 nm) resolves roughly 1 arcminute.