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In celestial navigation, lunar distance, also called a lunar, is the angular distance between the Moon and another celestial body. The lunar distances method uses this angle and a nautical almanac to calculate Greenwich time if so desired, or by extension any other time. That calculated time can be used in solving a spherical triangle.
The instantaneous precision of the Lunar Laser Ranging experiments can achieve small millimeter resolution, and is the most reliable method of determining the lunar distance. The semi-major axis is determined to be 384,399.0 km. [ 10 ]
The lunar distance is the angle between a suitable star and the Moon. The dotted lines show the distances between Aldebaran and the Moon, 5 hours apart. Moon not to scale. "Lunars" or lunar distances were an early proposal for the calculation of longitude, having been first made practical by Regiomontanus in his 1474 Ephemerides Astronomicae.
An older but still useful and practical method of determining accurate time at sea before the advent of precise timekeeping and satellite-based time systems is called "lunar distances," or "lunars," which was used extensively for a short period and refined for daily use on board ships in the 18th century. Use declined through the middle of the ...
In the eighteenth and nineteenth centuries, navigational tables based on lunar theory, initially in the Nautical Almanac, were much used for the determination of longitude at sea by the method of lunar distances.
Lunar Laser Ranging (LLR) is the practice of measuring the distance between the surfaces of the Earth and the Moon using laser ranging. The distance can be calculated from the round-trip time of laser light pulses travelling at the speed of light , which are reflected back to Earth by the Moon's surface or by one of several retroreflectors ...
The longitude rewards were the system of inducement prizes offered by the British government for a simple and practical method for the precise determination of a ship's longitude at sea. The prizes, established through an act of Parliament, the Longitude Act 1714 ( 13 Ann. c. 14), in 1714, were administered by the Board of Longitude .
In this work, Werner also proposed an astronomical method to determine longitude, by measuring the position of the moon relative to the background stars. The idea was later discussed in detail by Petrus Apianus in his Cosmographicus liber (Landshut 1524) and became known as the lunar distance method .