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垂直圈是天文学中用于测量角度的光学仪器，其名称源自球面几何学中垂直圈的数学概念。垂直圈可以用于定义天体的高度角，一个天体的高度角是从地平圈起，沿垂直圈到其所在位置的弧距。^[1]它由一个望远镜组成，望远镜安装在水平倾斜轴上，由一个稳定的方位角支架支撑，可以在高度和方位角上旋转。使用精细划分的大圆和读数显微镜测量围绕倾斜轴和立轴的角运动。^[2]

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子午儀

参考文献

^ Ashworth, William B. Scientist of the day - Jesse RAMSDEN. Linda Hall Library. 2019-11-05 [2025-01-05]. Ramsden’s most famous instrument is a five-foot vertical transit circle, made for the astronomical observatory at Palermo, Sicily, and commissioned by the future director of the Observatory, Giuseppe Piazzi. [..] The vertical circle measures altitude, and the horizontal circle at the bottom measures azimuth.
^ Chauvenet, William. A Manual of Spherical and Practical Astronomy. II: Theory and use of astronomical instruments. Philadelphia: J.B. Lippincott & Co. 1863: 315. Chapter VII. The Altitude and Azimuth Instrument. [..] Sometimes the horizontal circle is reduced to small and designed simply as a finder or to set the instrument approximately at a given azimuth while the vertical is made of unusually large dimensions and is intended for most refined astronomical measurement. The instrument is then known simply as a vertical circle. Such is the ERTEL Vertical Circle of the Pulkova Observatory, the telescope of which has a focal length of 77 inches, and its vertical circle a diameter of 43 inches.

[1] Ashworth, William B. Scientist of the day - Jesse RAMSDEN. Linda Hall Library. 2019-11-05 [2025-01-05]. Ramsden’s most famous instrument is a five-foot vertical transit circle, made for the astronomical observatory at Palermo, Sicily, and commissioned by the future director of the Observatory, Giuseppe Piazzi. [..] The vertical circle measures altitude, and the horizontal circle at the bottom measures azimuth.

[2] Chauvenet, William. A Manual of Spherical and Practical Astronomy. II: Theory and use of astronomical instruments. Philadelphia: J.B. Lippincott & Co. 1863: 315. Chapter VII. The Altitude and Azimuth Instrument. [..] Sometimes the horizontal circle is reduced to small and designed simply as a finder or to set the instrument approximately at a given azimuth while the vertical is made of unusually large dimensions and is intended for most refined astronomical measurement. The instrument is then known simply as a vertical circle. Such is the ERTEL Vertical Circle of the Pulkova Observatory, the telescope of which has a focal length of 77 inches, and its vertical circle a diameter of 43 inches.

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垂直圈 (仪器)

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参考文献

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