An ancient instrument for solving problems relating to time and the position of the Sun and stars in the sky. It had many uses, including telling time during the day or night, finding the time of sunrise and sunset and, thus, the length of the day, and locating celestial objects in the sky. It was widely used until replaced by the → sextant. The → planispheric astrolabe, which is the most common type of the instrument, is typically made up of a graduated disk hanging vertically, which is rotated so that it can be directed to the star chosen. The local time can thus be read from the face of the astrolabe, and different tables, at various latitudes, can be used. More specifically, a planispheric astrolabe is made up of the following main components: → mater, → tympanum, → rete, → alidade, → throne, → limb, → pin, → horse, → front, and → back. The astrolabe was invented by Greeks, and some historians have attributed it to Hipparchus (c190-c120 BC). Modern, sophisticated versions (such as → prismatic astrolabe and → Danjon astrolabe), are used for high precision measurements of star positions. See also → particular astrolabe, → spherical astrolabe, and → universal astrolabe.
M.E., from O.Fr. astrelabe, from M.L. astrolabium, from Gk. astrolabos (organon) "star taking (instrument)," from astron "star," → astro- + lambanein "to take."
Ostorlâb, from Ar. usturlab, from Gk. astrolabos, as above.
One who practices → astrology; one who professes to foretell events by the aspects and situation of the stars.
Agent noun from → astrology.
Axtargu, a classical term used by e.g. Jalâleddin Rumi (Mowlavi), 13th century poet, → astrology.
A → pseudoscience based on the belief that the apparent positions and → aspects of a small number of celestial bodies influence the course of human life and terrestrial events. Although the Sun and Moon have a gravitational influence on Earth, there is no known force that can cause celestial bodies to affect human affairs in the way claimed by → astrologers. Generally speaking, astrology is baseless and incoherent. In the astrological belief the influence of celestial bodies does not depend upon their distance from Earth, but on their positions and apparent angular separations. Outer planets can have a similar degree of influence as the inner planets. As a consequence, the billions of planets in our Galaxy and in billions of other galaxies should also influence us, and logically the effect of those planets must overwhelm any influence of the planets we see. Nevertheless astrologers do not care, and this fact makes astrological deductions absurd even in their scheme. Historically, the planets → Uranus, → Neptune, and → Pluto were not used in astrological predictions. They were added from the 18th century onward, after their discovery. Now that Pluto is disqualified as a planet, will astrologers remove it from their theories? If the answer is negative, they must logically include the numerous other similar → dwarf planets (such as → Charon, → Quaoar, → Sedna) residing in the → Kuiper belt. In brief, astrology is a superstition chiefly based on ignorance and man's need for mental contentment.
Axtarguyi, literally "star-telling," from axtar "star," → astro- + guyi verbal noun from goftan "to tell, speak, talk;" Mid.Pers. guftan "to say, tell, utter;" O.Pers. gaub- "to say."
Fr.: binaire astrométrique
A binary star in which the presence of an unresolved companion is revealed by small oscillations in the movement of the visible component caused by the gravitational influence of the unseen component.
The precise measurement of the positions and motions of → astronomical objects.
Axtarsanji, from axtar, → astro-, + -sanji "measuring."
fazânavard (#), keyhânnavard (#)
Fr.: astronaute, cosmonaute
A person trained to pilot, navigate, or otherwise participate as a crew member of a spacecraft.
Astronaut, from Gk. → astro- "star" + nautes "sailor," from naus "ship" (cognate with Mod.Pers. nâv "ship;" Av./O.Pers. *nāv-, O.Pers. nāviyā- "fleet;" Skt. nau-, nava- "ship, boat;" Gk. naus, neus, L. navis; PIE *nāu- "ship").
Fazânavard, from Ar. fazâ "space" + navard agent
noun from navardidan "to travel, walk, pass by
fazânavardi (#), keyhânnavardi (#)
The science and technology of space flight, including the building and operation of space vehicles.
Axtaršenâs has a long history in Persian; it is abundantly used by Ferdowsi (A.D. 950-1020) in his great work Šâhnâmé (Shahnameh); from axtar "star" → astro- + šenâs contraction of šenâsandé "expert, knowlegeable, skilled," from šenâxtan "to know, to recognize." → astronomy.
axtaršenâxti, axtaršenâsik, axtari (#)
Of or relating to → astronomy.
Fr.: horloge astronomique
A precise pendulum clock with separate dials for seconds, minutes, and hours. It was originally used by astronomers to calculate astronomical time.
pâyâ-ye axtaršenâsik, ~ axtaršenâxti (#)
Fr.: constante astronomique
hamârâhâ-ye axtaršenâsik, ~ axtarsršnâxti (#)
Fr.: coordonnées astronomiques
Values in a reference system used to relate the position of a body on the celestial sphere.
Fr.: horizon astronomique
The intersection of a plane perpendicular to the radius of the Earth through the observer's eye with the celestial sphere. Same as → true horizon. Because the → celestial sphere has an infinite radius, two observers at different heights above sea level, but placed on the same vertical line, have the same astronomical horizon. Because of → dip of the horizon, the astronomical horizon always lies above the → sea horizon. But on land it is usually hidden by trees, hills, and buildings which determine the observer's → apparent horizon.
Fr.: instrument astronomique
A device used to observe and study → astronomical objects.
Fr.: latitude astronomique
barâxt-e axtaršenâsik, ~ axtari
Fr.: objet astronomique
A naturally occurring physical entity or association that lies beyond the Earth's atmosphere and can be studied observationally. In other words, a gravitationally bound structure that is associated with a position in space, but may consist of multiple independent astronomical objects. A list of astronomical objects includes → planets, → asteroids, → comets, → stars, → nebulae, galaxies (→ galaxy), → galaxy clusters, → pulsars, and → black holes. Note that → celestial body, → celestial object, and → heavenly body are less technical terms for these entities.
nepâhesgâh-e axtaršenâsik, ~ axtaršenâxti
Fr.: observatoire astronomique
A building, place, or institution designed and equipped for making → observations of astronomical phenomena.
Fr.: réfraction astronomique
sit-e axtaršenâsik, ~ axtaršenâxti
Fr.: site astronomique
A certain place whose characteristics, as to location, altitude, atmospheric conditions, etc., make it appropriate for astronomical observations.
Fr.: table astronomique
One of a set of tables giving parameters used for calculations of positions of the Sun, the Moon, and the planets in particular in pre-telescopic astronomy. The oldest known astronomical tables are those of Ptolemy. In Modern astronomy it is usually replaced by the term → ephemeris. Same as → zij. See also → Toledan Tables, → Alfonsine Tables.