The theoretical limit for resolution comes from diffraction. It is a function of the wavelength of light being observed, and the size of the telescope. This is

The theoretical limit for resolution comes from diffraction. It is a function of the wavelength of light being observed, and the size of the telescope. This is measured by the Rayleigh criterion For a telescope with a circular apeture, the resolution is given by aproximatly R ~ 1.22 λ/D where: * λ is the wavelength * D is the diameter * 1.22 is the first zero of the intensity function for the Airy Disk