With larger aperture, a telescope mirror or lens is capable of showing fainter objects due to the increased light grasp. In addition, it’s also capable of showing more minute detail. The ability to see fine detail is referred-to as resolving power, or simply resolution. It’s measured in terms of the ability to split (see as separate objects) a double star system where the components are both around 6^th magnitude. The larger the telescope, the closer the stars can be to each other and still be split. This assumes that the quality of the optics is good enough to provide pinpoint images of the stars and that atmospheric conditions and other factors are ideal. In this respect, a telescope of a given size is said to resolve to the Dawes limit based on criteria established by the astronomer William R. Dawes. The formula for resolution is 5.0" (arcseconds) divided by the aperture of the telescope in inches. As an example, a 4-inch telescope should resolve a double star whose components are separated by no less than about 1.25".