Brandis Sextant with Willson Bubble Telescope

First-generation aeronautical sextants  had a bubble level to help the navigator locate the horizon in hazy or cloudy conditions. The instruments were hard to handle with air blowing past at 160 kilometers (100 miles) per hour.

Caption:
A maritime sextant with a special bubble attachment to the eyepiece to aid in establishing a horizon in aeronautical use, circa 1919.
Type: Artifact
Image Date: January 18, 2013
Credit: National Air and Space Museum, Smithsonian Institution.
Origin: National Air and Space Museum, Smithsonian Institution.
Creator: Eric Long
NASM2013-00222
 
A maritime sextant with a special bubble attachment to the eyepiece to aid in establishing a horizon in aeronautical use, circa 1919.