The resolution of terrestrial optical telescopes are limited by steadiness of the atmosphere through which they peer. Because the atmosphere is moving about due to winds and convection. Typical sights seldom allow telescopes to resolve objects much smaller that 0.5 seconds of arc in diameter. Radio telescopes do not suffer similar distortion. Radio waves are refracted little as they pass through our atmosphere. As a result, large radio telescope's resolution is limited only by the size of the radio reflector relative to the wavelength of the observed radio signal. The largest single dishes can resovle features as small as 1/10th of a second of arc. Significantly better than optical telescopes.