The bubble octant and bubble sextant are air navigation instruments. Although an instrument is called a "bubble sextant", it may actually be a bubble octant.
Use
Ships had long used
sextant
A sextant is a doubly reflecting navigation instrument that measures the angular distance between two visible objects. The primary use of a sextant is to measure the angle between an astronomical object and the horizon for the purposes of cel ...
s for navigation, but sextants had problems in aircraft navigation.
A ship at sea is on a relatively flat surface and can use the horizon to measure the altitude of celestial objects.
An aircraft may not have the sea's horizon as a flat reference surface. It may be flying over land where the horizon is formed by mountains of unknown height.
A solution to the problem was to use a bubble to determine the reference plane.
The bubble in an airplane is subject to the plane's acceleration. If the plane is in sharp turn, the bubble will be displaced. Consequently, when the navigator is using a bubble sextant, the pilot tries to fly the plane straight and level.
Even when flying straight and level, the plane is subject to accelerations from density and wind changes. Consequently, many readings are taken and then averaged for a more accurate result. Some bubble octants have accessories to make the averaging simpler.
Development
Isaac Newton
Sir Isaac Newton (25 December 1642 – 20 March 1726/27) was an English mathematician, physicist, astronomer, alchemist, theologian, and author (described in his time as a " natural philosopher"), widely recognised as one of the g ...
developed the quadrant.
The octant was a further improvement. It could measure altitudes of up to 90° above the horizon.
The
sextant
A sextant is a doubly reflecting navigation instrument that measures the angular distance between two visible objects. The primary use of a sextant is to measure the angle between an astronomical object and the horizon for the purposes of cel ...
became the standard navigation instrument for ships. It could measure altitudes of up to about 120 degrees. That allowed the navigator to sight the horizon in front and measure the altitude of a star that was slightly behind.
The first bubble instruments were bubble sextants copying the features of an ordinary sextant. However, a bubble instrument does not view the horizon, so it never needs to measure an angle >90°. Modern instruments are technically bubble octants, though they may be labelled bubble sextants.
Gago Coutinho developed the first bubble sextant.
See also
*
Amelia Earhart
Amelia Mary Earhart ( , born July 24, 1897; disappeared July 2, 1937; Presumption of death, declared dead January 5, 1939) was an American aviation pioneer and writer. Earhart was the first women in aviation, female aviator to fly solo acro ...
. Her navigator,
Fred Noonan
Frederick Joseph "Fred" Noonan (born April 4, 1893 – disappeared July 2, 1937, declared dead June 20, 1938) was an American flight navigator, sea captain and aviation pioneer, who first charted many commercial airline routes across the Pacifi ...
, used a bubble octant.
*
Eddie Rickenbacker
Edward Vernon Rickenbacker or Eddie Rickenbacker (October 8, 1890 – July 23, 1973) was an American fighter pilot in World War I and a Medal of Honor recipient.Aircraft Sextant Smithsonian Institution.
*
*
"Bubble sextant" Smithsonian Institution.
Bausch and Lomb
Bausch + Lomb is an eye health products company based in Vaughan, Ontario, Canada. It is one of the world's largest suppliers of contact lenses, lens care products, pharmaceuticals, intraocular lenses, and other eye surgery products. The compan ...
type 23
*
*
*
* {{cite patent , inventor1-first=G. B. , inventor1-last=Gallasch , inventor2-first=H. F. , inventor2-last=Kurtz , title=Sextant , country=US , patent-number=2080851 , ref=none
Air navigationCelestial navigationNavigational equipment