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Aperture masking interferometry (AMI) is a technique of increasing the angular resolution of a telescope by means of an aperture mask, a mask with separated holes that effectively turns a single telescope into an interferometer. While the mask can be right at the telescope's aperture, there are methods of locating it further along the optical path. A cost is that the light collection area of the telescope is much reduced so it is effective only for bright sources. Interferometers are often cited as having the angular resolution of a telescope with an aperture the width of its longest baseline, but with enough effort and with some restriction on the pattern of baselines, this can be exceeded. It requires some post-processing, now typically done by computer, to reconstruct the image from interference fringe patterns. It can be considered a sophisticated version of apodization using masking. The practicality and utility of this technique has grown over time, due to the advent and practicality of CCDs, which increases the light sensitivity of telescopes, and through the continuing reduction in the cost of computation. AMI is used by numerous major research telescopes, including the Subaru Telescope, Keck Observatory, and the James Webb Space Telescope.