六分仪
外观
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![](http://178.128.105.246/host-http-upload.wikimedia.org/wikipedia/commons/thumb/a/a7/Sextant.jpg/220px-Sextant.jpg)
![](http://178.128.105.246/host-http-upload.wikimedia.org/wikipedia/commons/thumb/6/6a/Sekstant.jpg/220px-Sekstant.jpg)
![](http://178.128.105.246/host-http-upload.wikimedia.org/wikipedia/commons/thumb/7/76/Using_sextant_swing.gif/220px-Using_sextant_swing.gif)
![](http://178.128.105.246/host-http-upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Marine_sextant.svg/220px-Marine_sextant.svg.png)
六分仪(sextant),在测绘和船舶通信导航中,是由分度弧、指标臂、指标镜、水平镜、望远镜和测微鼓组成,弧长约为圆周的六分之一,用以观察天体高度和目标的水平角与垂直角的反射镜类型的手持测角仪器。广泛用于航海和航空中,用来确定观测者的自身位置。
历史
[编辑]六分仪的原理由伊萨克·牛顿提出,1732年,英国海军开始将原始仪器安装在船艇上。其光学原理主要以“在同一个平面上,经过两次反射之光线,其最初方向和最终方向之夹角为两反射面夹角的两倍。”。因此,初期六分仪的最大测量角度是90度(经过两次反射之夹角为两反射面的两倍),故六分仪的仪弧设计为45度,约为1/8圆,称为八分仪。1757年,约翰·坎贝尔船长将八分仪的测量夹角提高到120度,也就是六分仪的仪弧设计为60度,约为1/6圆,正式更名为六分仪,现今所使用的六分仪可测量之夹角已提高到120度以上,但还是称为六分仪。
参考文献
[编辑]- Bowditch, Nathaniel. The American Practical Navigator. Bethesda, MD: National Imagery and Mapping Agency. 2002 [2017-06-21]. ISBN 0-939837-54-4. (原始内容存档于2007-06-24).
- Cutler, Thomas J. Dutton's Nautical Navigation 15th. Annapolis, MD: Naval Institute Press. December 2003. ISBN 978-1-55750-248-3.
- Department of the Air Force. Air Navigation (PDF). Department of the Air Force. March 2001 [2014-12-28]. (原始内容存档 (PDF)于2020-09-17).
- Great Britain Ministry of Defence (Navy). Admiralty Manual of Seamanship. The Stationery Office. 1995. ISBN 0-11-772696-6.
- Encyclopædia Britannica. Navigation. Chisholm, Hugh (编). Encyclopædia Britannica 19 11th: 284–298. 1911 [2015-01-25].
- Encyclopædia Britannica. Sextant. Chisholm, Hugh (编). Encyclopædia Britannica 24 11th: 749–751. 1911 [2015-01-25].
- Maloney, Elbert S. Chapman Piloting and Seamanship 64th. New York: Hearst Communications. December 2003. ISBN 1-58816-089-0.
参见
[编辑]外部连接
[编辑]- Her Majesty's Nautical Almanac Office
- The History of HM Nautical Almanac Office(页面存档备份,存于互联网档案馆)
- Chapter 17 from the online edition of Nathaniel Bowditch's American Practical Navigator (页面存档备份,存于互联网档案馆)
- CD-Sextant - Build your own sextant(页面存档备份,存于互联网档案馆) Simple do-it-yourself project.
- Lunars web site. online calculation
- Complete celnav theory book, including Lunars(页面存档备份,存于互联网档案馆)