垂直圈 (儀器)

垂直圈是天文學中用於測量角度的光學儀器，其名稱源自球面幾何學中垂直圈的數學概念。垂直圈可以用於定義天體的高度角，一個天體的高度角是從地平圈起，沿垂直圈到其所在位置的弧距。^[1]它由一個望遠鏡組成，望遠鏡安裝在水平傾斜軸上，由一個穩定的方位角支架支撐，可以在高度和方位角上旋轉。使用精細劃分的大圓和讀數顯微鏡測量圍繞傾斜軸和立軸的角運動。^[2]

參見

子午儀

參考文獻

^ 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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