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Star Transit
A star transit is the passage of a star across the field of view of a telescope eyepiece. The precise observation of star transits is the basis of many methods in astronomy and in geodesy. The measurements can be done in different ways: # visually (mostly up to 1990): accuracy 0,1" to 2" (depending on the instrument); timing with digital clocks about 0,05–0,2 seconds # by CCD and other electro-optical sensors: as above, time often better # semi automatic instruments: Photography or "impersonal micrometer", ca. 2 times better than No.1 # by Scanning methods: Astrometry satellites like Hipparcos about 0,01". See also * Accuracy and precision * Instrument error * Meridian circle * Minute and second of arc * Theodolite * Transit instrument Literature * Karl Ramsayer, 1969: '' Geodätische Astronomie'', Vol.2a of Handbuch der Vermessungskunde, 900 p., J.B. Metzler-Verlag Stuttgart. * Ivan I. Mueller, 1969: Spherical and Practical Astronomy as applied to Geodesy, 610 p., Fred.Unga ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Accuracy And Precision
Accuracy and precision are two measures of ''observational error''. ''Accuracy'' is how close a given set of measurements ( observations or readings) are to their '' true value'', while ''precision'' is how close the measurements are to each other. In other words, ''precision'' is a description of '' random errors'', a measure of statistical variability. ''Accuracy'' has two definitions: # More commonly, it is a description of only ''systematic errors'', a measure of statistical bias of a given measure of central tendency; low accuracy causes a difference between a result and a true value; ISO calls this ''trueness''. # Alternatively, ISO defines accuracy as describing a combination of both types of observational error (random and systematic), so high accuracy requires both high precision and high trueness. In the first, more common definition of "accuracy" above, the concept is independent of "precision", so a particular set of data can be said to be accurate, precise, both, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Practical Astronomy
Pragmatism is a philosophical tradition that considers words and thought as tools and instruments for prediction, problem solving, and action, and rejects the idea that the function of thought is to describe, represent, or mirror reality. Pragmatists contend that most philosophical topics—such as the nature of knowledge, language, concepts, meaning, belief, and science—are all best viewed in terms of their practical uses and successes. Pragmatism began in the United States in the 1870s. Its origins are often attributed to the philosophers Charles Sanders Peirce, William James, and John Dewey. In 1878, Peirce described it in his pragmatic maxim: "Consider the practical effects of the objects of your conception. Then, your conception of those effects is the whole of your conception of the object."Peirce, C.S. (1878), " How to Make Our Ideas Clear", ''Popular Science Monthly'', v. 12, 286–302. Reprinted often, including ''Collected Papers'' v. 5, paragraphs 388–410 and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ivan I
Ivan I may refer to: *Ivan I Debranin, first Archbishop of Ochrid (11th-century) *Ivan I of Moscow (1288–1340), Prince of Moscow *Ivan I Crnojević Ivan () is a Slavic male given name, connected with the variant of the Greek name (English: John) from Hebrew meaning 'God is gracious'. It is associated worldwide with Slavic countries. The earliest person known to bear the name was Bulgari ... of Zeta (r. 1465–1490) {{hndis, Ivan 01 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geodetic Astronomy
Geodetic astronomy or astronomical geodesy (astro-geodesy) is the application of astronomical methods into geodetic networks and other technical projects of geodesy. Applications The most important applications are: * Establishment of geodetic datum systems (e.g. ED50) or at expeditions * apparent places of stars, and their proper motions * precise astronomical navigation * astro-geodetic geoid determination * modelling the rock densities of the topography and of geological layers in the subsurface * Monitoring of the Earth rotation and polar wandering * Contribution to the time system of physics and geosciences Measuring techniques Important measuring techniques are: * Latitude determination and longitude determination, by theodolites, tacheometers, astrolabes or zenith cameras * time and star positions by observation of star transits, e.g. by meridian circles (visual, photographic or CCD) * Azimuth determination ** for the exact orientation of geodetic networks ** for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Karl Ramsayer
Karl Ramsayer (29 September 1911, Schwäbisch Gmünd''Große Kreisstadt Schwäbisch Gmünd. Personalia'' in ''ostalb einhorn. Vierteljahreshefte für Heimat und Kultur im Ostalbkreis'', Nr. 37/38, Arbeitsgemeinschaft Einhorn-Verlag E. Dietenberger GmbH und Ostalbverlag – Schwäbischer Heimatverlag Dietenberger & Theiss oHG, Schwäbisch Gmünd und Aalen, 1983, P. 148 – 24 December 1982, near Stuttgart) was a German geodesist and is well known as one of the most important scientists in geodetic astronomy and in electronic navigation. In the 1950s Ramsayer became professor at the Geodetic Institute of the University of Stuttgart. In the following years he founded the ''Institut für Navigation'' which he developed to a leading research institute in the fields of avionics. Many patents in automatic positioning methods and air guidance systems have their origin in Stuttgart research projects. Work on navigation and geodesy Much of Ramsayer's research on navigation concerned d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transit Instrument
In astronomy, a transit instrument is a small telescope with extremely precisely graduated mount used for the precise observation of star positions. They were previously widely used in astronomical observatories and naval observatories to measure star positions in order to compile nautical almanacs for use by mariners for celestial navigation, and observe star transits to set extremely accurate clocks ( astronomical regulators) which were used to set marine chronometers carried on ships to determine longitude, and as primary time standards before atomic clocks. The instruments can be divided into three groups: meridian, zenith, and universal instruments. Types Meridian instruments For observation of star transits in the exact direction of South or North: * Meridian circles, Mural quadrants etc. * Passage instruments (transportable, also for prime vertical transits) Zenith instruments * Zenith telescope * Photozenith tube (PZT) * zenith cameras * Danjon astrolabe, Zeis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theodolite
A theodolite () is a precision optical instrument for measuring angles between designated visible points in the horizontal and vertical planes. The traditional use has been for land surveying, but it is also used extensively for building and infrastructure construction, and some specialized applications such as meteorology and rocket launching. It consists of a moveable telescope mounted so it can rotate around horizontal and vertical axes and provide angular readouts. These indicate the orientation of the telescope, and are used to relate the first point sighted through the telescope to subsequent sightings of other points from the same theodolite position. These angles can be measured with accuracies down to microradians or seconds of arc. From these readings a plan can be drawn, or objects can be positioned in accordance with an existing plan. The modern theodolite has evolved into what is known as a total station where angles and distances are measured electronically ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Minute And Second Of Arc
A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The nautical mile (nmi) was originally defined as the arc length of a minute of latitude on a spherical Earth, so the actual Earth circumference is very near . A minute of arc is of a radian. A second of arc, arcsecond (arcsec), or arc second, denoted by the symbol , is of an arcminute, of a degree, of a turn, and (about ) of a radian. These units originated in Babylonian astronomy as sexagesimal subdivisions of the degree; they are used in fields that involve very small angles, such as astronomy, optometry, ophthalmology, optics, navigation, land surveying, and marksmanship. To express even smaller angles, standard SI prefixes can be employed; the milliarcsecond (mas) and microarcsecond (μas), for instance, are commonly us ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meridian Circle
The meridian circle is an instrument for timing of the passage of stars across the local meridian, an event known as a culmination, while at the same time measuring their angular distance from the nadir. These are special purpose telescopes mounted so as to allow pointing only in the meridian, the great circle through the north point of the horizon, the north celestial pole, the zenith, the south point of the horizon, the south celestial pole, and the nadir. Meridian telescopes rely on the rotation of the sky to bring objects into their field of view and are mounted on a fixed, horizontal, east–west axis. The similar transit instrument, transit circle, or transit telescope is likewise mounted on a horizontal axis, but the axis need not be fixed in the east–west direction. For instance, a surveyor's theodolite can function as a transit instrument if its telescope is capable of a full revolution about the horizontal axis. Meridian circles are often called by these names, alth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Instrument Error
Instrument error refers to the error of a measuring instrument, or the difference between the actual value and the value indicated by the instrument. There can be errors of various types, and the overall error is the sum of the individual errors. Types of errors include * systematic errors * random errors * absolute error * other error Systematic errors The size of the systematic error is sometimes referred to as the accuracy. For example the instrument may always indicate a value 5% higher than the actual value; or perhaps the relationship between the indicated and actual values may be more complicated than that. A systematic error may arise because the instrument has been incorrectly calibrated, or perhaps because a defect has arisen in the instrument since it was calibrated. Instruments should be calibrated against a standard instrument that is known to be accurate, and ideally the calibration should be repeated at intervals. The most rigorous standards are those maintained b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
