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Douglas-Appleyard Arcless Sextant

 

 

 

 

 

 

 

Douglas-Appleyard sextantSir Henry Percy Douglas was joint inventor of the Douglas-Appleyard Arcless Sextant.

The Douglss-Appleyard arcless sextant is an English instrument designed for use in surveying and in aerial navigation. The sextant has the usual index and horizon mirrors and telescope. The index arm and graduated arc of the marine sextant are discarded, and the index mirror is operated by a worm gear and worm. The worm carries a micrometer drum and a counter, the counter showing tens of degrees and the micrometer drum graduated scale divided to intervals of 10 minutes, A. small magnifying glass is provided which is mounted in such a way that the instrument may be read without removing the eye from the telescope. Electric illumination is furnished. It is claimed that fair accuracy is obtainable in a very sport space of time and that the instrument is well suited for aerial navigation.



 

 

 

 

 

 

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Last modified: Saturday, 18 March 2017