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Bubble Sextant - click to enlarge

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Bubble Sextant

Catalogue number:
NASM 1965-128

"BRANDIS & SONS, INC. / BROOKLYN, N.Y. / 206C-134" and "AERONAUTICAL OCTANT / MARK 1 MODEL 4 / BU. AERO SERIAL 40-31." The telescope is marked "WILLSON TELESCOPE / PATENT 1705146 / OTHER PAT. PENDING 2080-122"

radius 5.25 inches

This is a small left-handed octant with a Willson bubble telescope, a Fischer rapid release lever, a drum micrometer, electric light over the bubble and divided arc, battery in the handle, and radium illuminator for star observations. Since the legs are on the front of the frame, the octant can be set down with the handle uppermost. The Navy Bureau of Aeronautics designated this the Mark I, Model 4. The pending patent has not been identified.

This was the 134th example of the Model 206C, and the 40th example made for the Navy in 1931. The Navy transferred it to the Smithsonian in 1963.

Ref: R. W. Willson, "Instrument Including Means for Determining the Horizontal Direction," U.S. patent #1,705,146

Pioneer Instrument Co., "Aircraft Octant, Type 206 with Willson Bubble Telescope, Instructions," and "Appendix to Instructions for Octant Mark I, Model 4."

Further Information:

Aircraft Sextant