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Almucantar
An almucantar (also spelled almucantarat or almacantara) is a circle on the celestial sphere parallel to the horizon. Two stars that lie on the same almucantar have the same altitude. The term was introduced into European astronomy by monastic astronomer Hermann Contractus of Reichenau, Latinized from the Arabic word ' ("the almucantar, sundial", plural: '), derived from ' ("arch, bridge") Almucantar staff An almucantar staff is an instrument chiefly used to determine the time of sunrise and sunset, in order to find the amplitude and consequently the variations of the compass. Usually made of pear tree or boxwood, with an arch of 15° to 30°,May, William Edward, ''A History of Marine Navigation'', G. T. Foulis & Co. Ltd., Henley-on-Thames, Oxfordshire, 1973, it is an example of a backstaff. The sun casts that shadow of a vane (B in the adjacent image) on a ''horizon vane'' (A). The horizon vane has a slit or hole to allow the observer to see the horizon in the distanc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Almucantar-staff
An almucantar (also spelled almucantarat or almacantara) is a circle on the celestial sphere parallel to the horizon. Two stars that lie on the same almucantar have the same altitude. The term was introduced into European astronomy by monastic astronomer Hermann Contractus of Reichenau, Latinized from the Arabic word ' ("the almucantar, sundial", plural: '), derived from ' ("arch, bridge") Almucantar staff An almucantar staff is an instrument chiefly used to determine the time of sunrise and sunset, in order to find the amplitude and consequently the variations of the compass. Usually made of pear tree or boxwood, with an arch of 15° to 30°,May, William Edward, ''A History of Marine Navigation'', G. T. Foulis & Co. Ltd., Henley-on-Thames, Oxfordshire, 1973, it is an example of a backstaff. The sun casts that shadow of a vane (B in the adjacent image) on a ''horizon vane'' (A). The horizon vane has a slit or hole to allow the observer to see the horizon in the distanc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Almucantarat (it)
An almucantar (also spelled almucantarat or almacantara) is a circle on the celestial sphere parallel to the horizon. Two stars that lie on the same almucantar have the same altitude. The term was introduced into European astronomy by monastic astronomer Hermann Contractus of Reichenau, Latinized from the Arabic word ' ("the almucantar, sundial", plural: '), derived from ' ("arch, bridge") Almucantar staff An almucantar staff is an instrument chiefly used to determine the time of sunrise and sunset, in order to find the amplitude and consequently the variations of the compass. Usually made of pear tree or boxwood, with an arch of 15° to 30°,May, William Edward, ''A History of Marine Navigation'', G. T. Foulis & Co. Ltd., Henley-on-Thames, Oxfordshire, 1973, it is an example of a backstaff. The sun casts that shadow of a vane (B in the adjacent image) on a ''horizon vane'' (A). The horizon vane has a slit or hole to allow the observer to see the horizon in the distanc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Backstaff
The backstaff is a navigational instrument that was used to measure the altitude of a celestial body, in particular the Sun or Moon. When observing the Sun, users kept the Sun to their back (hence the name) and observed the shadow cast by the upper vane on a horizon vane. It was invented by the English navigator John Davis, who described it in his book ''Seaman's Secrets'' in 1594. Types of backstaffs 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. Many types of instruments evolved from the cross-staff that can be classified as backstaves. Only the Davis quadrant remains dominant in the history of navigation instruments. Indeed, the Davis quadrant is essentially synonymous with backstaff. However, Davis was neither the first nor the last to design such an instrument and others are considered here ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circle Of Equal Altitude
The circle of equal altitude, also called circle of position (CoP), is defined as the locus of points on Earth on which an observer sees a celestial object such as the sun or a star, at a given time, with the same observed altitude. It was discovered by the American sea-captain Thomas Hubbard Sumner in 1837, published in 1843 and is the basis of an important method in celestial navigation Discovery Sumner discovered the line on a voyage from South Carolina to Greenock in Scotland in 1837. On December 17, as he was nearing the coast of Wales, he was uncertain of his position after several days of cloudy weather and no sights. A momentary opening in the clouds allowed him to determine the altidude of the sun. This, together with the chronometer time and the latitude enabled him to calculate the longitude. But he was not confident of his latitude, which depended on dead reckoning (DR). So he calculated longitude using his DR value and two more values of latitude 10' and 20' to the no ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Measuring Instruments
A measuring instrument is a device to measure a physical quantity. In the physical sciences, quality assurance, and engineering, measurement is the activity of obtaining and comparing physical quantities of real-world objects and events. Established standard objects and events are used as units, and the process of measurement gives a number relating the item under study and the referenced unit of measurement. Measuring instruments, and formal test methods which define the instrument's use, are the means by which these relations of numbers are obtained. All measuring instruments are subject to varying degrees of instrument error and measurement uncertainty. These instruments may range from simple objects such as rulers and stopwatches to electron microscopes and particle accelerators. Virtual instrumentation is widely used in the development of modern measuring instruments. Time In the past, a common time measuring instrument was the sundial. Today, the usual measuring instru ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomical Coordinate Systems
Astronomical coordinate systems are organized arrangements for specifying positions of satellites, planets, stars, galaxies, and other celestial objects relative to physical reference points available to a situated observer (e.g. the true horizon and north cardinal direction to an observer situated on the Earth's surface). Coordinate systems in astronomy can specify an object's position in three-dimensional space or plot merely its direction on a celestial sphere, if the object's distance is unknown or trivial. Spherical coordinates, projected on the celestial sphere, are analogous to the geographic coordinate system used on the surface of Earth. These differ in their choice of fundamental plane, which divides the celestial sphere into two equal hemispheres along a great circle. Rectangular coordinates, in appropriate units, have the same fundamental () plane and primary (-axis) direction, such as a rotation axis. Each coordinate system is named after its choice of fundamental ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Applied Optics
''Applied Optics'' is a peer-reviewed scientific journal published by The Optical Society three times a month. It was established in 1962 with John N. Howard as founding editor-in-chief. The journal covers all aspects of optics, photonics, imaging, and sensing. According to the ''Journal Citation Reports'', the journal has a 2021 impact factor The impact factor (IF) or journal impact factor (JIF) of an academic journal is a scientometric index calculated by Clarivate that reflects the yearly mean number of citations of articles published in the last two years in a given journal, as i ... of 1.905. References External links * {{Official website, http://www.osapublishing.org/ao/ Optics journals Optica (society) academic journals English-language journals Publications established in 1962 Journals published between 27 and 51 times per year ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Journal Of Geophysical Research
The ''Journal of Geophysical Research'' is a peer-reviewed scientific journal. It is the flagship journal of the American Geophysical Union. It contains original research on the physical, chemical, and biological processes that contribute to the understanding of the Earth, Sun, and Solar System. It has seven sections: A (Space Physics), B (Solid Earth), C (Oceans), D (Atmospheres), E (Planets), F (Earth Surface), and G (Biogeosciences). All current and back issues are available online for subscribers. History The journal was originally founded under the name ''Terrestrial Magnetism'' by the American Geophysical Union's president Louis Agricola Bauer in 1896. It was renamed to ''Terrestrial Magnetism and Atmospheric Electricity'' in 1899 and in 1948 it acquired its current name. In 1980, three specialized sections were established: ''A: Space Physics'', ''B: Solid Earth'', and ''C: Oceans''. Subsequently, further sections have been added: ''D: Atmospheres'' in 1984, ''E: Planets'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Teruyuki Nakajima
Teruyuki (written: 照幸, 照之 or 晃之) is a masculine Japanese given name. Notable people with the name include: *Teruyuki Hashimoto, Japanese mixed martial artist *, Japanese actor *, Japanese footballer *, Japanese karateka *, Japanese comedian, ''tarento Television personalities in Japan, known as in Japanese, are celebrities who regularly appear in mass media in Japan, especially as panelists on variety shows. During the Golden Age of Hollywood, bankable stars in America were described as "tal ...'' and TV presenter {{given name Japanese masculine given names ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oleg Dubovik
Oleg (russian: Олег), Oleh ( uk, Олег), or Aleh ( be, Алег) is an East Slavic given name. The name is very common in Russia, Ukraine and Belаrus. It derives from the Old Norse ''Helgi'' ( Helge), meaning "holy", "sacred", or "blessed". The feminine equivalent is Olga. While Germanic in origin, "Oleg" is not very common outside Eastern European countries. Russian pronunciation Олег (Oleg) is pronounced ˈlʲekin Russian. The English pronunciation of Oleg is based on the transliteration of the Cyrillic alphabet, and overlooks three key features of the Russian pronunciation: # The stress is on the second syllable. In spoken Russian, the initial short unstressed 'O' is reduced to similar to the 'a' as in 'about'. # The 'л' (l) becomes palatalized to ʲ─ that is, it gains a 'y'-like quality, and but is still most closely approximated by a plain English 'l'. # The word-final final 'г' (g) is devoiced to Thus, rather than "Oh-leg", the phonetically clo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photometer
A photometer is an instrument that measures the strength of electromagnetic radiation in the range from ultraviolet to infrared and including the visible spectrum. Most photometers convert light into an electric current using a photoresistor, photodiode, or photomultiplier. Photometers measure: *Illuminance *Irradiance *Light absorption * Scattering of light *Reflection of light *Fluorescence *Phosphorescence *Luminescence History Before electronic light sensitive elements were developed, photometry was done by estimation by the eye. The relative luminous flux of a source was compared with a standard source. The photometer is placed such that the illuminance from the source being investigated is equal to the standard source, as the human eye can judge equal illuminance. The relative luminous fluxes can then be calculated as the illuminance decreases proportionally to the inverse square of distance. A standard example of such a photometer consists of a piece of paper with an o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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