Accession No
2182
Brief Description
bubble sextant, Air Ministry Mark V, by the Royal Aircraft Establishment (R.A.E.), English, 1919
Origin
England
Maker
Royal Aircraft Establishment (R.A.E.)
Class
navigation
Earliest Date
1919
Latest Date
1919
Inscription Date
Material
metal; glass; plastic (ivorine); wood
Dimensions
length 175mm; breadth 170mm; height 81mm
Special Collection
Provenance
Transferred from Department of Geography, University of Cambridge, Cambridge, England, 05/1969.
Inscription
‘R.A.E. SEXTANT MK V
NO 19
PAT: NO 26291/19’
Description Notes
Bubble sextant, Mark V, by the Royal Aircraft Establishment (R.A.E.), English, 1919.
Black-painted metal plates and casing. Index glass, two shades on pivoted arm. Telescopic sight. Drum divided -3 - 38, subdivided ot 10´, and 38 - 80, subdivided to 10´. Light for reading scale, with electric socket. Turned wooden handle. Ivorine table for recording readings, headed ‘TIME’ in ‘Mins’ and ‘Secs’ and ‘ALTITUDE’ in ‘Degr’s’ and ‘Mins’.
Condition
References
Events
Description
The principal difficulty when navigating from an aircraft is the absence of a horizon which is often obscured by clouds. In 1918 the Royal Aircraft Establishment (RAE) developed a sextant using a bubble level as an artificial horizon.
The bubble horizon consists of a fluid container bounded by a plano-convex lens on its upper side, and a plane glass on its lower side; in this a bubble is formed. There are two stainless steel mirrors and a collimating lens. By adjusting the mirrors and the bubble lens system, keeping the bubble approximately central within its container, the observer looking into the collimating lens will see an image of the bubble, whose centre will always appear to be on the horizon. A series of observations are made and averaged out to diminish any error due to the vibration, acceleration and motion of the aircraft itself.
04/08/2008
Created by: Dr Anita McConnell on 04/08/2008
FM:44421
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