@college level). Optical resolution means the ability to tell 2 bright spots apart. The number is inversely proportional to aperture or diameter of the lens or mirror of the telescope or camera. The smaller the resolution number the better. A 100 mm scope has angular resolution of 1.2 arc second while a 200 mm one has 0.6 arc second, assuming 1)same manufacture precision 2)ignore air particles/current detrimental effects(absent in space condition)3)The image sensors(film, CCD,Cmos..)have matching resolution.