ROYAL ASTRONOMICAL SOCIETY / SCIENCE PHOTO LIBRARY ROYAL ASTRONOMICAL SOCIETY / SCIENCE PHOTO LIBRARY
November 1887. This telescope is on an altazimuth mount. An altazimuth is used to measure the altitude (from the horizon) and azimuth (angle from north) of a star. These measurements can then be used to calculate the precise position of the star. Unlike a transit circle telescope, an altazimuth telescope can be pointed at any region of the sky, using a complicated mechanism to move the telescope. This telescope, at Oakfield, Bittern, near Southampton, UK, was operated by British astronomer Major T. A. Skelton (left).
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