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World's oldest known sundial, from Egypt's Valley of the Kings (c. 1500 BC), used to measure work hours. [1] [2] [3]A sundial is a device that indicates time by using a light spot or shadow cast by the position of the Sun on a reference scale. [4]
An astronomical instrument is a device for observing, measuring, or recording astronomical data. [ citation needed ] They are used in the scientific field of astronomy , a natural science that studies celestial objects and the phenomena that occur in the cosmos, with the object of explaining their origin and evolution over time.
Actual sunset: Two minutes before the Sun disappears below the horizon. Sunset (or sundown) is the disappearance of the Sun at the end of the Sun path, below the horizon of the Earth (or any other astronomical object in the Solar System) due to its rotation.
If the style is fixed, the line on the dial plate perpendicularly beneath the style is called the substyle, [6] meaning "below the style". The angle the style makes with the plane of the dial plate is called the substyle height, an unusual use of the word height to mean an angle. On many wall dials, the substyle is not the same as the noon line ...
A merkhet (Science Museum, London)The merkhet or merjet (Ancient Egyptian: mrḫt, 'instrument of knowing' [1]) was an ancient surveying and timekeeping instrument. It involved the use of a bar with a plumb line, attached to a wooden handle. [2]
Misra Yantra (meaning mixed instrument, it is a compilation of five different instruments) Nadi Valaya Yantra (two sundials on different faces of the instrument, the two faces representing north and south hemispheres; measuring the time to an accuracy of less than a minute) [11] Palbha Yantra
Backstaff is the name given to any instrument that measures the altitude of the sun by the projection of a shadow. It appears that the idea for measuring the sun's altitude using back observations originated with Thomas Harriot. [2]
Burt's solar compass or astronomical compass/sun compass is a surveying instrument that makes use of the Sun's direction instead of magnetism. William Austin Burt invented his solar compass in 1835. The solar compass works on the principle that the direction to the Sun at a specified time can be calculated if the position of the observer on the ...