"Astrolabe An astrolabe ( ""astrolabos""; ""al-Asturlāb""; ""Akhtaryab"") is an elaborate inclinometer, historically used by astronomers and navigators to measure the inclined position in the sky of a celestial body, day or night. The word astrolabe means ""the one that catches the heavenly bodies."" It can thus be used to identify stars or planets, to determine local latitude given local time (and vice versa), to survey, or to triangulate. It was used in classical antiquity, the Islamic Golden Age, the European Middle Ages and the Age of Discovery for all these purposes. The astrolabe's importance not only comes from the early"
"Today, 126 such instruments remain worldwide, the oldest from the 11th century. The altitude of the sun, or the Right Ascension and Declination of stars could be calculated with these by inputting the location of the observer on the meridian ring of the globe. An armillary sphere had similar applications. No early Islamic armillary spheres survive, but several treatises on ""the instrument with the rings"" were written. In this context there is also an Islamic development, the spherical astrolabe, of which only one complete instrument, from the 14th century, has survived. Brass astrolabes were a Hellenistic invention. The first Islamic"
"the very intense Sun. The maritime (navigation) version of these devices being skeletal in design rather than solid sheet form, so as to limit buffeting or displacement of the instrument while in the operators hand from wind exposure. http://www.astrolabeproject.com/26/01/2014/deconstructing-the-sine-quadrant-part-1-introduction/ Sine quadrant The sine quadrant (Arabic: Rub‘ul mujayyab, الربع المجيب) was a type of quadrant used by medieval Arabic astronomers. It is also known as a ""sinecal quadrant"" in the English-speaking world. The instrument could be used to measure celestial angles, to tell time, to find directions, or to determine the apparent positions of any celestial object for any time. The"
"and longitude to every place on his maps. From the late 9th century CE, the Arabian Kamal was used in equatorial regions, to measure the height of Polaris above the horizon. This instrument could only be used in latitudes close to the horizon. The Mariner's astrolabe which gives the angle of the Sun from the horizon at noon, or the angle of a known star at night, was used from around the 15th to the 17th century. The observation of the Sun instead of Polaris enabled the measurement of latitude in the Southern hemisphere but required the use of solar"
"as the orientation of planets gave insight to zodiac signs which helped some doctors cater medical treatments to patients. At least 15 minutes was needed to calculate the planetary position with the use of a table for each celestial body. A horoscope of that era would have required the positions of seven astronomical objects, requiring nearly two hours of manual calculation time. Equatorium An equatorium (plural, equatoria) is an astronomical calculating instrument. It can be used for finding the positions of the Moon, Sun, and planets without calculation, using a geometrical model to represent the position of a given celestial"
"development of astronomy, but is also effective for determining latitude on land or calm seas. Although it is less reliable on the heaving deck of a ship in rough seas, the mariner's astrolabe was developed to solve that problem. OED gives the translation ""star-taker"" for the English word ""astrolabe"" and traces it through medieval Latin to the Greek word ""astrolabos"", from ""astron"" ""star"" and ""lambanein"" ""to take"". In the medieval Islamic world the Arabic word """"al-Asturlāb"""" (i.e. astrolabe) was given various etymologies. In Arabic texts, the word is translated as """"ākhdhu al-Nujuum"""" (, lit. ""star-taker""), a direct translation of the"
"based on findings of earlier Arab astronomers. Al-Farghani gave revised values for the obliquity of the ecliptic, the precessional movement of the apogees of the sun and the moon, and the circumference of the earth. The books were widely circulated through the Muslim world, and even translated into Latin. The earliest surviving astrolabe is constructed by Islamic mathematician-astronomer Mohammad al-Fazari. Astrolabes are the most advanced instruments of their time. The precise measurement of the positions of stars and planets allows Islamic astronomers to compile the most detailed almanacs and star atlases yet. Abū Rayḥān al-Bīrūnī discussed the Indian heliocentric theories"
"plotting of current location and anticipated destination, as a result a number of techniques and instruments were employed in order to ensure the accuracy of a reading. Designed to work in concert with a quadrant, which came to replace the kamal entirely in the 14th century, the mariner's astrolabe also measured the altitude of celestial bodies; however this tool could use the sun as a reference point as well thus allowing for the continual plotting of a ship's course in day or night. It also had the ability to determine latitude in rough seas, an essential ability for long distance"
"world. About 550 AD, Christian philosopher John Philoponus wrote a treatise on the astrolabe in Greek, which is the earliest extant treatise on the instrument. The earliest description of the spherical astrolabe dates back to the Persian astronomer Nayrizi (fl. 892–902). Muslim astronomers also independently invented the celestial globe, which were used primarily for solving problems in celestial astronomy. Today, 126 such instruments remain worldwide, the oldest from the 11th century. The altitude of the sun, or the Right Ascension and Declination of stars could be calculated with these by inputting the location of the observer on the meridian ring"
"lunar mansions were determined by the armillary sphere since the seventh century or so. There was also a celestial globe rotated by flowing water."" An instrument invented by the mathematician and astronomer Bhaskara II (1114–1185 CE) consisted of a rectangular board with a pin and an index arm. This device—called the ""Phalaka-yantra""—was used to determine time from the sun's altitude. The ""Kapālayantra"" was an equatorial sundial instrument used to determine the sun's azimuth. ""Kartarī-yantra"" combined two semicircular board instruments to give rise to a 'scissors instrument'. Introduced from the Islamic world and first finding mention in the works of Mahendra"
"Equatorial ring An equatorial ring was an astronomical instrument used in the Hellenistic world to determine the exact moment of the spring and autumn equinoxes. Equatorial rings were placed before the temples in Alexandria, in Rhodes, and perhaps in other places, for calendar purposes. The easiest way to understand the use of an equatorial ring is to imagine a ring placed vertically in the east-west plane at the Earth's equator. At the time of the equinoxes, the Sun will rise precisely in the east, move across the zenith, and set precisely in the west. Throughout the day, the bottom half"
"the Arab world accordingly. Al-Qibjāqī also reports that sailors in the Indian Ocean used iron fish instead of needles. Late in the 13th century, the Yemeni Sultan and astronomer al-Malik al-Ashraf described the use of the compass as a ""Qibla indicator"" to find the direction to Mecca. In a treatise about astrolabes and sundials, al-Ashraf includes several paragraphs on the construction of a compass bowl (ṭāsa). He then uses the compass to determine the north point, the meridian (khaṭṭ niṣf al-nahār), and the Qibla. This is the first mention of a compass in a medieval Islamic scientific text and its"
"instrument by the theodolite. Dioptra A dioptra (sometimes also named dioptre or diopter from ) is a classical astronomical and surveying instrument, dating from the 3rd century BCE. The dioptra was a sighting tube or, alternatively, a rod with a sight at both ends, attached to a stand. If fitted with protractors, it could be used to measure angles. Greek astronomers used the dioptra to measure the positions of stars; both Euclid and Geminus refer to the dioptra in their astronomical works. By the time of Ptolemy (2nd century CE), it was obsolete as an astronomical instrument, having been replaced"
"and declination. Once good star catalogs were available a transit telescope could be used anywhere in the world to accurately measure local longitude and time by observing local meridian transit times of catalogue stars. Prior to the invention of the atomic clock this was the most reliable source of accurate time. In the ""Almagest"", Ptolemy describes a meridian circle which consisted of a fixed graduated outer ring and a movable inner ring with tabs that used a shadow to set the Sun's position. It was mounted vertically and aligned with the meridian. The instrument was used to measure the altitude"
"Mariner's astrolabe The mariner's astrolabe, also called sea astrolabe, was an inclinometer used to determine the latitude of a ship at sea by measuring the sun's noon altitude (declination) or the meridian altitude of a star of known declination. Not an astrolabe proper, the mariner's astrolabe was rather a graduated circle with an alidade used to measure vertical angles. They were designed to allow for their use on boats in rough water and/or in heavy winds, which astrolabes are ill-equipped to handle. In the sixteenth century, the instrument was also called a ring. Many dates can be found for the"
"Meteorological astrology Meteorological astrology or astrometeorology (from Greek , ""astron"", ""constellation, star""; , ""metéōros"", ""high in the sky""; and , ""-logia"") is the practice of applying the astrological/astronomical placements of the Sun, Moon, and planets to attempt to forecast the weather. Astrometeorology is thousands of years old and based on astronomical positions that allegedly directly affect the weather on Earth. Ancient classical astrologers created weather forecasting known as meteorology by noting the positions of stars, planets, the Sun, and Moon. According to their texts, when planets occupy constellations as seen from Earth, and that are harmonious to one another, or"
"Equatorium An equatorium (plural, equatoria) is an astronomical calculating instrument. It can be used for finding the positions of the Moon, Sun, and planets without calculation, using a geometrical model to represent the position of a given celestial body. The earliest extant record of a solar equatorium, that is, one to find the position of the sun, is found in Proclus's fifth-century work ""Hypostasis"", where he gives instructions on how to construct one in wood or bronze. Although planetary equatoria were also probably made by the ancient Greeks, the first surviving description of one is from the ""Libros del saber"
"Sine quadrant The sine quadrant (Arabic: Rub‘ul mujayyab, الربع المجيب) was a type of quadrant used by medieval Arabic astronomers. It is also known as a ""sinecal quadrant"" in the English-speaking world. The instrument could be used to measure celestial angles, to tell time, to find directions, or to determine the apparent positions of any celestial object for any time. The name is derived from the Arabic ""rub‘‘‘"" meaning a quarter and ""mujayyab"" meaning marked with sine. It was described, according to King, by Muhammad ibn Mūsā al-Khwārizmī in 9th century Baghdad. The instrument is a quarter of a circle"
"his treatise, indicating that metal astrolabes were known in the Christian East well before they were developed in the Islamic world or in the Latin West. Astrolabes were further developed in the medieval Islamic world, where Muslim astronomers introduced angular scales to the design, adding circles indicating azimuths on the horizon. It was widely used throughout the Muslim world, chiefly as an aid to navigation and as a way of finding the Qibla, the direction of Mecca. Eighth-century mathematician Muhammad al-Fazari is the first person credited with building the astrolabe in the Islamic world. The mathematical background was established by"
"Muslim astronomer Albatenius in his treatise ""Kitab az-Zij"" (c. 920 AD), which was translated into Latin by Plato Tiburtinus (""De Motu Stellarum""). The earliest surviving astrolabe is dated AH 315 (927–28 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, navigation, surveying, timekeeping, prayer, Salat, Qibla, etc. The spherical astrolabe was a variation of both the astrolabe and the armillary sphere, invented"
"used to determine the boundaries of astronomical constellations that lie in the vicinity of the zodiac, which are, and always have been, irregular in their size and shape. The convention of measuring celestial longitude within individual signs was still being used in the mid-19th century, but modern astronomy now numbers degrees of celestial longitude from 0° to 360°, rather than 0° to 30° within each sign. The use of the zodiac as a means to determine astronomical measurement remained the main method for defining celestial positions by Western astronomers until the Renaissance, at which time preference moved to the equatorial"
"the Hagia Sofia mosque in Istanbul. It was used for the observation of the Sun, Moon, and other celestial bodies, and along with other sophisticated equipment such as an armillary and an astrolabe, the astronomers working in Samarkand could determine noon every day according to the meridional height of the Sun, distance from the zenith and declination. By 1437, scholarly studies using the observatory had updated the Ilkhanic Tables which had previously been observed in the 1260s and 1270s at the Maragheh observatory, which provided valuable sine and tangent tables, and the Zij-i Sultani, which displayed improved planetary parameters and"
"navigation, but mostly for timekeeping. Islam requires its followers to pray five times a day, at specific position of the Sun in the sky. As such, accurate observations of the Sun and its trajectory on the sky were needed. In the late 10th century, Iranian astronomer Abu-Mahmud Khojandi built a massive observatory near Tehran. There, he took accurate measurements of a series of meridian transits of the Sun, which he later used to calculate the obliquity of the ecliptic. Following the fall of the Western Roman Empire, Western Europe was cut from all sources of ancient scientific knowledge, especially those"
"positions of the Sun, Moon, and planets and other astronomical data, as well as tables of lunar distances giving the distance of the Moon from the Sun and nine stars suitable for lunar observations (ten stars for the first few years). This publication later became the standard almanac for mariners worldwide. Since it was based on the Royal Observatory, it helped lead to the international adoption a century later of the Greenwich Meridian as an international standard. Another proposed solution was to use a mechanical timepiece, to be carried on a ship, that would maintain the correct time at a"
"The astronomical position calculated from an ephemeris is given in the spherical polar coordinate system of right ascension and declination. Some of the astronomical phenomena of interest to astronomers are eclipses, apparent retrograde motion/planetary stations, planetary es, sidereal time, positions for the mean and true nodes of the moon, the phases of the Moon, and the positions of minor celestial bodies such as Chiron. Ephemerides are used in celestial navigation and astronomy. They are also used by some astrologers. For scientific uses, a modern planetary ephemeris comprises software that generates positions of planets and often of their satellites, asteroids, or"
"ibn al-Shatir. Several forms of quadrants were invented by Muslims. Among them was the sine quadrant used for astronomical calculations, and various forms of the horary quadrant, used to determine time (especially the times of prayer) by observations of the sun or stars. A center of the development of quadrants was ninth-century Baghdad. The Equatorium is an Islamic invention from Al-Andalus. The earliest known was made in the 11th century. It is a mechanical device for finding the positions of the moon, sun, stars and planets, without calculation using a geometrical model to represent the celestial body's mean and anomalistic"
"90 degree point. The third and most commonly seen configuration of the ""torquetum"" uses all its assets to make measurements. The upper portion is now set at an angle equal to the obliquity of the ecliptic, which allows the instrument to give ecliptic coordinates. This measures the celestial bodies now on celestial latitude and longitude scales which allow for greater precision and accuracy in making measurements. These three differing configurations allowed for added convenience in taking readings and made once tedious and complicated measuring more streamlined and simple. Torquetum The torquetum or turquet is a medieval astronomical instrument designed to"
"Dioptra A dioptra (sometimes also named dioptre or diopter from ) is a classical astronomical and surveying instrument, dating from the 3rd century BCE. The dioptra was a sighting tube or, alternatively, a rod with a sight at both ends, attached to a stand. If fitted with protractors, it could be used to measure angles. Greek astronomers used the dioptra to measure the positions of stars; both Euclid and Geminus refer to the dioptra in their astronomical works. By the time of Ptolemy (2nd century CE), it was obsolete as an astronomical instrument, having been replaced by the armillary sphere."
"them to track the motions of the planets and the inferred position of the Sun. The motion of the Sun against the background stars (and the horizon) was used to create calendars, which could be used to regulate agricultural practices. The Gregorian calendar, currently used nearly everywhere in the world, is a solar calendar based on the angle of the Earth's rotational axis relative to its local star, the Sun. The oldest accurately dated star chart was the result of ancient Egyptian astronomy in 1534 BC. The earliest known star catalogues were compiled by the ancient Babylonian astronomers of Mesopotamia"
"in all of science, is the measurement of the positions of celestial objects. Historically, accurate knowledge of the positions of the Sun, Moon, planets and stars has been essential in celestial navigation (the use of celestial objects to guide navigation) and in the making of calendars. Careful measurement of the positions of the planets has led to a solid understanding of gravitational perturbations, and an ability to determine past and future positions of the planets with great accuracy, a field known as celestial mechanics. More recently the tracking of near-Earth objects will allow for predictions of close encounters or potential"
"the past when a single specified celestial body, whether the Sun or a selected star, rises or sets at the measured azimuth. The astronomer, Norman Lockyer, applied this method to Stonehenge by measuring the orientation of the Stonehenge avenue and comparing it to the position of solstitial sunrise, which changes slowly due to the changing obliquity of the ecliptic. The archaeologist, F. C. Penrose, applied a similar method to ancient Greek Temples, attempting to establish their dates by relating their orientation to the appearance of stars on the horizon, the position of which changes slowly due to the precession of"
"Astronomical clock An astronomical clock is a clock with special mechanisms and dials to display astronomical information, such as the relative positions of the sun, moon, zodiacal constellations, and sometimes major planets. The term is loosely used to refer to any clock that shows, in addition to the time of day, astronomical information. This could include the location of the sun and moon in the sky, the age and Lunar phases, the position of the sun on the ecliptic and the current zodiac sign, the sidereal time, and other astronomical data such as the moon's nodes (for indicating eclipses) or"
"Toledan Tables The Toledan Tables, or Tables of Toledo, were astronomical tables which were used to predict the movements of the Sun, Moon and planets relative to the fixed stars. They were completed around year 1080 by a group of Arabic astronomers at Toledo, Spain. They had started as preexisting Arabic tables made elsewhere, and were numerically adjusted to be centered on the location of Toledo. In modern English astronomy, tables of movements of astronomical bodies are called ephemerides. The Tables of Toledo were partly based on the work of al-Zarqali (known to the West as Arzachel), an Arab mathematician,"