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The term angular magnification is used for magnifying instruments (telescopes, microscopes) that include an eyepiece. When two points are visible through the telescope (i.e., through its eyepiece), the angular distance between them appears larger than that when viewed without the telescope from the same location, making the view through the telescope appear larger. The ratio of the apparent angular distance between such points with the telescope to the actual angular distance without it the telescope's angular magnification.
Commonly, the word magnification applied to telescopes and binoculars refers to angular magnification. However, for optics not providing direct viewing through an eyepiece (such as an opaque projector), magnification has the specific meaning of the ratio of the size of an image with the size of the object itself. For research astronomical telescopes photographing or otherwise sensing the image, the plate scale and angular resolution are the quantities of interest rather than magnification.