What is the theoretical maximum resolution of a single telescope?
For a single telescope, its resolution (the finest details it can distinguish) is limited by the diffraction of light as it passes through the telescope’s aperture. The resolution is improved if the wavelength of the light gets shorter or the telescope diameter gets larger. Since the wavelength may be fixed by the kind of astrophysical observations that are needed, this is one reason why astronomers try to build larger telescopes. This fundamental limit on the sharpness of a telescope’s vision is called the diffraction limit, and telescopes that reach it are diffraction-limited. The sharpness of a telescope’s vision may be worse in practice than this ideal value. For example, at visible light wavelengths, atmospheric turbulence will further degrade the telescope resolution. Technology such as adaptive optics can allow telescopes to overcome atmospheric turbulence and approach diffraction-limited resolution. Telescope resolution can be measured by the angular size of the smallest detail
