![]() Things that look a lot like diffraction gratings, orderly arrays of equally-spaced objects, are found in nature these are crystals. As you get further from the objects, however, they will eventually merge to become one. Up close, then, two objects are easily resolved. The closer you are to two objects, the greater the angular separation between them. The factor of 1.22 applies to circular apertures like your pupil, a telescope, or a camera lens. The minimum angular separation is given by: A telescope, or even a camera, has a much larger aperture, and therefore more resolving power. The size of the central peak in the diffraction pattern depends on the size of the aperture (the opening you look through). Once the two central peaks start to overlap, in other words, the two objects look like one. The limit is when one central peak falls at the position of the first dark fringe for the second diffraction pattern. You are able to resolve the two objects as long as the central peaks in the two diffraction patterns don't overlap. For two far-away objects separated by a small angle, the diffraction patterns will overlap. If you look at a far-away object, the image of the object will form a diffraction pattern on your retina. ![]() So, why does the telescope resolve the stars into separate objects while your eye can not? It's all because of diffraction. You can only see that they are two stars by looking at them through a telescope. Some stars, however, are so close together that they look like one star. If you look at two stars in the sky, for example, you can tell they are two stars if they're separated by a large enough angle. The resolving power of an optical instrument, such as your eye, or a telescope, is its ability to separate far-away objects that are close together into individual images, as opposed to a single merged image. ![]()
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