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Bubble Quadrant - click to enlarge

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Bubble Quadrant

Catalogue number:
NASM 1957-633


The Aeronautical Instruments Section of the National Bureau of Standards tested an instrument of this sort in the early 1920s and declared it the best of the several German instruments known. It has a telescope along one side, an index arm pivoted at the center of the arc, and a bubble tube mounted on the index arm. A mirror in the telescope reflects an image of the bubble into the eyepiece. The scale is graduated every degree from -20o to +100o and read by micrometer to 30 seconds of arc. The National Bureau of Standards transferred this example to the Smithsonian in 1957.

Ref: K. H. Beij, "Astronomical Methods in Aerial Navigation," Report of the National Advisory Committee for Aeronautics 198 (1924), p. 14.

W. Lindt, "Ein Libellenquadrant in neuer Form fΓΌr Astronomische Ortsbestimmungen," Deutsche Luftfahrer Zeitschrift 16 (May 29, 1912): 273-274.

Further Information:

Aircraft Sextant