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Cammenga lensatic compass The M-1950 U.S. military lensatic field compass with self-luminous lighting (designated the Model 3H by Cammenga) is fitted with self-luminous tritium vial lighting. Under U.S. military specification (MIL-SPEC) performance criteria, ten pre-production samples of the M-1950 are required to meet a battery of performance ...
Classic geological compass (Brunton), sideview Classic geological compass (Brunton), topview. There are a number of different specialized magnetic compasses used by geologists to measure orientation of geological structures, as they map in the field, to analyze and document the geometry of bedding planes, joints, and/or metamorphic foliations and lineations.
Model of a lodestone compass from Han dynasty. Some claims state that the first compasses in ancient Han dynasty China were made of lodestone, a naturally magnetized ore of iron. [2] [16] The earliest mention of a needle's attraction appears in a work composed between 20 and 100 AD, the Lunheng (Balanced Inquiries): "A lodestone attracts a needle."
The pilot may use this pointer to home directly towards the beacon, or may also use the magnetic compass and calculate the direction from the beacon (the radial) at which their aircraft is located. Unlike the RDF, the ADF operates without direct intervention, and continuously displays the direction of the tuned beacon.
Tritium is found on several military models of compass that are sold to civilians (Silva of Sweden, Suunto, and Cammenga all make tritium models). Unlike radium-base paint, tritium gas emits only low energy beta particles (electrons) that are unable to penetrate the borosilicate glass walls of its capsule.
The liquid compass is a design in which the magnetized needle or card is damped by fluid to protect against excessive swing or wobble, improving readability while reducing wear. A rudimentary working model of a liquid compass was introduced by Sir Edmond Halley at a meeting of the Royal Society in 1690. [88]
The Earth's axis of rotation remains effectively stationary throughout the year. Thus, with knowledge of the current time and geographical position in the form of latitude and longitude, which are set on the instrument using dials, an astrocompass can be sighted onto any astronomical object with a known position to give an extremely accurate reading.
Compass turns (turns using the magnetic compass as the primary reference instrument) are not standard practice in modern aircraft. Compass turns are typically performed in simulated or actual failures of the directional gyro or other navigational instruments. A magnetic compass is a simple instrument when the compass is not moving and is on the ...