Information about Astrolabe

The astrolabe is a historical astronomical instrument used by classical astronomers, navigators, and astrologers. Its many uses included locating and predicting the positions of the Sun, Moon, planets and stars; determining local time given local longitude and vice-versa; surveying; and triangulation. In the Islamic world, they are and were used primarily for astronomical studies, though astrology was often involved there as well. Astrologers of the European nations used astrolabes to construct horoscopes.

There is often confusion between the astrolabe and the mariner's astrolabe. While the astrolabe could be useful for determining latitude on land, it was an awkward instrument for use on the heaving deck of a ship or in wind. The mariner's astrolabe was developed to address these issues.

A Brief History

The astrolabe was invented in the Hellenistic world in either the first or second centuries BCE and is often attributed to Hipparchus. A marriage of the planisphere and dioptra, the astrolabe was effectively an analog calculator capable of working out several different kinds of problems in spherical astronomy. Theon of Alexandria wrote a detailed treatise on the astrolabe, and Lewis (2001) argues that Ptolemy used an astrolabe to make the astronomical observations recorded in the Tetrabiblos.^[1]

Brass astrolabes (Persian: اسطرلاب asterlab, ostorlab) were developed in Islamic world, chiefly as an aid to navigation and as a way of finding the qibla, the direction of Mecca. The first person credited with building the astrolabe in the Islamic world is reportedly the 8th century Persian mathematician al-Fazari.^[2] The mathematical background was established by the Arab astronomer al-Battani in his treatise Kitab az-Zij (ca. 920 AD), which was translated into Latin by Plato Tiburtinus (De Motu Stellarum). The earliest surviving astrolabe is dated AH 315 (927/8 AD). In the Islamic world, astrolabes were used to find the times of sunrise and the rising of fixed stars, to help schedule morning prayers (salat). In the 10th century, al-Sufi first described over 1,000 different uses of an astrolabe, in areas as diverse as astronomy, astrology, horoscopes, navigation, surveying, timekeeping, prayer, Salah, Qibla, etc.^[3]

Arzachel (al-Zarqali) of al-Andalus constructed the first universal astrolabe instrument which, unlike its predecessors, did not depend on the latitude of the observer, and could be used from anywhere on the Earth. This instrument became known in Europe as the "Saphaea". The astrolabe was introduced to other parts of Europe via Islamic Spain in the 11th century. Early Christian recipients of Arab astronomy included Gerbert of Aurillac and Hermannus Contractus.

The English author Geoffrey Chaucer (ca. 1343–1400) compiled a treatise on the astrolabe for his son, mainly based on Messahalla. The same source was translated by the French astronomer and astrologer Pelerin de Prusse and others. The first printed book on the astrolabe was Composition and Use of Astrolabe by Cristannus de Prachaticz, also using Messahalla, but relatively original.

In 1370, the first Indian treatise on the astrolabe was written by the Jain astronomer Mahendra Suri.^[4]

The first known European metal astrolabe was developed in the 15th century by Rabbi Abraham Zacuto in Lisbon. Metal astrolabes improved on the accuracy of their wooden precursors. In the 15th century, the French instrument-maker Jean Fusoris (ca. 1365–1436) also started selling astrolabes in his shop in Paris, along with portable sundials and other popular scientific gadgets of the day.

In the 16th century, Johannes Stöffler published Elucidatio fabricae ususque astrolabii, a manual of the construction and use of the astrolabe. Four identical 16th century astrolabes made by Georg Hartmann provide some of the earliest evidence for batch production by division of labor.

Astrolabes and clocks

At first mechanical astronomical clocks were influenced by the astrolabe; in many ways they could be seen as clockwork astrolabes designed to produce a continual display of the current position of the sun, stars, and planets. For example, Richard of Wallingford's clock (c. 1330) consisted essentially of a star map rotating behind a fixed rete.

Many astronomical clocks, such as the famous clock at Prague, use an astrolabe-style display, adopting a stereographic projection (see below) of the ecliptic plane.

In 1985 Swiss watchmaker Dr. Ludwig Oechslin designed and built an astrolabe wristwatch in conjunction with Ulysse Nardin.

Construction

An astrolabe consists of a hollow disk, called the mater (mother), which is deep enough to hold one or more flat plates called tympans, or climates. A tympan is made for a specific latitude and is engraved with a stereographic projection of circular lines of equal azimuth and altitude representing the portion of the celestial sphere which is above the local horizon. The rim of the mater is typically graduated into hours of time, or degrees of arc, or both. Above the mater and tympan, the rete, a framework bearing a projection of the ecliptic plane and several pointers indicating the positions of the brightest stars, is free to rotate. Some astrolabes have a narrow rule which rotates over the rete, and may be marked with a scale of declinations.

The rete, representing the sky, has the function of a star chart. When it is rotated, the stars and the ecliptic move over the projection of the coordinates on the tympan. A complete rotation represents the passage of one day. The astrolabe is therefore a predecessor of the modern planisphere.

On the back of the mater there will often be engraved a number of scales which are useful in the astrolabe's various applications; these will vary from designer to designer, but might include curves for time conversions, a calendar for converting the day of the month to the sun's position on the ecliptic, trigonometric scales, and a graduation of 360 degrees around the back edge. Another ruler, called the alidade, is attached to the back face. When the astrolabe is held vertically, the alidade can be rotated and a star sighted along its length, so that the star's altitude in degrees can be read ("taken") from the graduated edge of the astrolabe; hence "astro" = star + "labe" = to take.

See also

• Antikythera mechanism
• Armillary sphere
• Astrarium
• Astrology
• Astronomical clock
• Cosmolabe
• Equatorium
• Islamic astronomy
• Orrery
• Planetarium
• Prague Orloj
• Sextant
• Sharafeddin Tusi, the inventor of the linear astrolabe
• Torquetum

References

• id="CITEREFEvans1998">Evans, James (1998), The History and Practice of Ancient Astronomy, Oxford University Press, ISBN 0195095391.
  • Alessandro Gunella and John Lamprey, Stoeffler's Elucidatio (translation of Elucidatio fabricae ususque astrolabii into English). Published by John Lamprey, 2007. lamprey@frii.com
  • id="CITEREFKrebsKrebs2003">Krebs, Robert E. & Carolyn A. Krebs (2003), Groundbreaking Scientific Experiments, Inventions, and Discoveries of the Ancient World, Greenwood Press.
    • id="CITEREFLewis2001">Lewis, M. J. T. (2001), Surveying Instruments of Greece and Rome, Cambridge University Press.
      • John North. God's Clockmaker, Richard of Wallingford and the invention of time. Hambledon and London, 2005.
      • Critical edition of Pelerin de Prusse on the Astrolabe (translation of Practique de Astralabe). Editors Edgar Laird, Robert Fischer. Binghamton, New York, 1995, in Medieval & Renaissance Texts & Studies. ISBN 0-86698-132-2
      • King, Henry Geared to the Stars: the evolution of planetariums, orreries, and astronomical clocks University of Toronto Press, 1978

      External links

      • The Astrolabe
      • Keith's Astrolabe, a software astrolabe simulator and tutorial written in Java
      • A working model of the Dr. Ludwig Oechslin's Astrolabium Galileo Galilei watch
      • Ulysse Nardin Astrolabium Galilei Galileo: A Detailed Explanation
      • Fully illustrated online catalogue of world's largest collection of astrolabes
      • Gerbert d'Aurillac's use of the Astrolabe at Convergence
      Three French ships have born the name Astrolabe, after the instument astrolabe and in honour of the preceeding ships:

      • The Astrolabe of Jean-François de Galaup, comte de La Pérouse (1781), a converted fluyt
      • The Astrolabe

      
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      Motto
      Unity in diversity^[1]
      Anthem
      O Arise, All You Sons^[2]
      
      

      
      Capital Port Moresby
      
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      Astrolabe Bay is a large body of water off the northern coast of Madang Province, Papua New Guinea, located at . It is a part of the Bismarck Sea and stretches from the Cape Iris in the south to the Cape Croisilles to the north.
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      mariner's astrolabe, also called sea astrolabe, is not an astrolabe proper, but rather a graduated circle with an alhidade used to measure vertical angles.

      History

      Many dates can be found for the appearance of the first mariner's astrolabes.
      ..... Click the link for more information.
      Astronomy is the scientific study of celestial objects (such as stars, planets, comets, and galaxies) and phenomena that originate outside the Earth's atmosphere (such as the cosmic background radiation).
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      Measuring instruments are the means by which this translation is made. All measuring instruments are subject to varying degrees of instrument error.
      
      Physicists use a vast range of instruments to perform their measurements.
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      Astronomy is the scientific study of celestial objects (such as stars, planets, comets, and galaxies) and phenomena that originate outside the Earth's atmosphere (such as the cosmic background radiation).
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      The Navigators is a worldwide Christian parachurch organization headquartered in Colorado Springs, Colorado. Its main purpose is the discipling (training) of Christians with a particular emphasis on enabling them to share their faith with others.
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      astrologer practices one or more forms of astrology. Typically an astrologer draws a horoscope for the time of an event, such as a person's birth, and interprets celestial points and their placements at the time of the event to better understand someone, determine the
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      The Sun
      
      Observation data
      Mean distance
      from Earth 1.49610¹¹ m
      (8.31 min at light speed)
      Visual brightness (V) −26.74^{m [1]}
      Absolute magnitude 4.
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      Moon  
      
      The Moon as seen by an observer on Earth
      Orbital characteristics
      Periapsis: 363,104 km
      0.0024 AU
      Apoapsis: 405,696 km
      0.0027 AU
      Semi-major axis: 384,399 km
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      planet, as defined by the International Astronomical Union (IAU), is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, not massive enough to cause thermonuclear fusion in its core, and has cleared its neighbouring region of
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      STARS can mean:

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      • Special Tactics And Rescue Service, a fictional task force that appears in Capcom's Resident Evil video game franchise.

      
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      equator divides the planet into a Northern Hemisphere and a Southern Hemisphere, and has a latitude of 0. Longitude is the east-west geographic coordinate measurement most commonly utilized in cartography and global navigation.
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      triangulation is the process of finding coordinates and distance to a point by calculating the length of one side of a triangle, given measurements of angles and sides of the triangle formed by that point and two other known reference points, using the law of sines.
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      During the Islamic Golden Age, usually dated from the 8th century to the 13th century,^[1] engineers, scholars and traders of the Islamic world contributed enormously to the arts, economics, industry, literature, navigation, philosophy, sciences, and technology, both by
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      Islamic astronomy or Arabic astronomy refers to the astronomical developments made by the Islamic civilization between the 8th and 17th centuries and written in Arabic.
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      Astrology (from Greek: αστήρ, αστρός (astér, astrós), "star", and λόγος, λόγου (lógos, lógou), "word" or "speech" lit.
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      cite any references or sources. Please help improve this article by citing reliable sources.
      * It may not present a worldwide view of the subject.
      * It may require general cleanup to meet Wikipedia's quality standards.
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      mariner's astrolabe, also called sea astrolabe, is not an astrolabe proper, but rather a graduated circle with an alhidade used to measure vertical angles.

      History

      Many dates can be found for the appearance of the first mariner's astrolabes.
      ..... Click the link for more information.
      The term Hellenistic (derived from Ἕλλην Héllēn, the Greeks' traditional self-described ethnic name) was established by the German historian Johann Gustav Droysen to refer to the spreading of
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      Hipparchus (Greek Ἵππαρχος; ca. 190 BC – ca. 120 BC) was a Greek astronomer, geographer, and mathematician of the Hellenistic period.
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      A planisphere is a star chart analog computer that can be adjusted to display the stars for any time and date. It is an instrument to learn how to recognize stars and constellations. The astrolabe is a predecessor of the modern planisphere.
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      A dioptra is an instrument dating back to the ancient Hellenistic civilization, since the 3rd century BCE. It is said to have been "long used by Greek astronomers", such as Hipparchus, sometimes credited with inventing it.
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      For other Theons (some of whom also worked in Alexandria) see Theon

      Theon (Greek: Θέων, ca. 335 - ca. 405 AD) was a Greek^[1] or Egyptian^[2]
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      Claudius Ptolemaeus (Greek: Κλαύδιος Πτολεμαῖος; after 83 – 161 AD), known in English as Ptolemy, was a Greek^[1] or Egyptian
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      fɒːɾˈsiː in Perso-Arabic script (Nasta`liq style):  
      Pronunciation: [fɒːɾˈsiː]
      Spoken in: Iran, Afghanistan, Tajikistan and areas of Uzbekistan and Pakistan.
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      During the Islamic Golden Age, usually dated from the 8th century to the 13th century,^[1] engineers, scholars and traders of the Islamic world contributed enormously to the arts, economics, industry, literature, navigation, philosophy, sciences, and technology, both by
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      Qibla (قبلة, also translated as Qiblah, Kibla or Kiblah) is an Arabic word for the direction that should be faced when a Muslim prays.
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      Makkah al-Mukarramah مكة المكرمة
      
      Location in the Kingdom of Saudi Arabia
      Coordinates:
      Province Makkah
      Government
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