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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.
David Winsta "Atmospheric Refraction and the Last Rays of the Setting Sun", reported at the Manchester Literary & Philosophical Society Meeting, 7 October 1873 Sir Arthur Schuster , Letter to NATURE , 21 February 1915, referring to his observation of the phenomenon on a voyage in the Indian Ocean in 1875
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 ...
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.
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]
North African, 9th century CE, planispheric astrolabe. Khalili Collection. A modern astrolabe made in 2013, in Tabriz, Iran.. An astrolabe (Ancient Greek: ἀστρολάβος astrolábos, ' star-taker '; Arabic: ٱلأَسْطُرلاب al-Asṭurlāb; Persian: ستارهیاب Setāreyāb) is an astronomical instrument dating to ancient times.
Heliophysics (from the prefix "helio", from Attic Greek hḗlios, meaning Sun, and the noun "physics": the science of matter and energy and their interactions) is the physics of the Sun and its connection with the Solar System. [1]
The heliotrope is an instrument that uses a mirror to reflect sunlight over great distances to mark the positions of participants in a land survey. The heliotrope was invented in 1821 by the German mathematician Carl Friedrich Gauss.