An ASTROLABE (Greek : ἀστρολάβος _astrolabos_;
While the astrolabe is effective for determining latitude on land or calm seas, it is less reliable on the heaving deck of a ship in rough seas. The mariner\'s astrolabe was developed to solve that problem.
* 1 Etymology
* 2 History
* 2.1 Ancient world * 2.2 Medieval era * 2.3 Astrolabes and clocks
* 3 Construction * 4 See also * 5 References * 6 External links
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
Al-Biruni quotes and criticizes the medieval scientist Hamzah al-Isfahani who had stated: "asturlab is an arabization of this Persian phrase" (_sitara yab_, meaning "taker of the stars"). In medieval Islamic sources, there is also a "fictional" and popular etymology of the words as "lines of lab". In this popular etymology , "Lab" is a certain son of Idris (=Enoch). This etymology is mentioned by a 10th-century scientist named al-Qummi but rejected by al-Khwarizmi .
An early astrolabe was invented in the Hellenistic world by
Apollonius of Perga , around 220 BC or in 150 BC and is often
Astrolabes continued in use in the Greek -speaking world throughout the Byzantine period. About 550 AD the Christian philosopher John Philoponus wrote a treatise on the astrolabe in Greek, which is the earliest extant Greek treatise on the instrument. In addition, Severus Sebokht , a bishop who lived in Mesopotamia, also wrote a treatise on the astrolabe in Syriac in the mid-7th century. Severus Sebokht refers in the introduction of his treatise to the astrolabe as being made of brass, indicating that metal astrolabes were known in the Christian East well before they were developed in the Islamic world or the Latin West.
A treatise explaining the importance of the astrolabe by Nasir
al-Din al-Tusi , Persian scientist.
Astrolabes were further developed in the medieval Islamic world ,
where Muslim astronomers introduced angular scales to the astrolabe,
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
The mathematical background was established by the 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 dated 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 ,
navigation , surveying , timekeeping , prayer ,
The spherical astrolabe , a variation of both the astrolabe and the
armillary sphere , was invented during the
Peter of Maricourt , in the last half of the 13th century, also wrote a treatise on the construction and use of a universal astrolabe (_Nova compositio astrolabii particularis_). Universal astrolabes can be found at the History of Science Museum in Oxford.
The English author Geoffrey Chaucer (c. 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 Pélerin de Prusse and others. The first printed book on the astrolabe was _Composition and Use of Astrolabe_ by Christian of Prachatice , also using Messahalla, but relatively original.
In 1370, the first Indian treatise on the astrolabe was written by the Jain astronomer Mahendra Suri .
The first known metal astrolabe in Western Europe is the Destombes astrolabe made from brass in tenth-century Spain. Metal astrolabes avoided the warping that large wooden astrolabes were prone to, allowing the construction of larger and therefore more accurate instruments. Metal astrolabes were also heavier than wooden instruments of the same size, making it difficult to use them as navigational instruments.
The astrolabe was almost certainly first brought north of the
Pyrenees by Gerbert of Aurillac (future
Pope Sylvester II ), where it
was integrated into the quadrivium at the school in Reims, France,
sometime before the turn of the 11th century. In the 15th century,
the French instrument-maker Jean Fusoris (fr) (c. 1365–1436) also
started remaking and selling astrolabes in his shop in
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
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 recent times, astrolabe watches have become a feature of haute horologie. For example, in 1985 Swiss watchmaker Dr. Ludwig Oechslin designed and built an astrolabe wristwatch in conjunction with Ulysse Nardin . Dutch watchmaker Christaan van der Klauuw also manufactures astrolabe watches today.
The Hartmann astrolabe in Yale collection. This instrument shows
its rete and rule. Celestial Globe,
An astrolabe consists of a 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 circles denoting azimuth and altitude and representing the portion of the celestial sphere above the local horizon. The rim of the mater is typically graduated into hours of time , 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. These pointers
are often just simple points, but depending on the skill of the
craftsman can be very elaborate and artistic. There are examples of
astrolabes with artistic pointers in the shape of balls, stars,
snakes, hands, dogs' heads, and leaves, among others. The names of
the indicated stars were often engraved on the pointers in
The rete, representing the sky , functions as a star chart . When it is rotated, the stars and the ecliptic move over the projection of the coordinates on the tympan. One complete rotation corresponds to the passage of a day. The astrolabe is therefore a predecessor of the modern planisphere .
On the back of the mater there is often engraved a number of scales that are useful in the astrolabe's various applications. These 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. The _alidade _ is attached to the back face. An alidade can be seen in the lower right illustration of the Persian astrolabe above. When the astrolabe is held vertically, the alidade can be rotated and the sun or a star sighted along its length, so that its altitude in degrees can be read ("taken") from the graduated edge of the astrolabe; hence the word's Greek roots: "astron" (ἄστρον) = star + "lab-" (λαβ-) = to take.
* ^ Modern editions of
John Philoponus ' treatise on the astrolabe
are _De usu astrolabii eiusque constructione libellus_ (On the Use and
Construction of the Astrolabe), ed. Heinrich Hase, Bonn: E. Weber,
* ^ O\'Leary, De Lacy (1948). _How Greek Science passed to the Arabs_. Routledge and Kegan Paul. "The most distinguished Syriac scholar of this later period was Severus Sebokht (d. 666–7), Bishop of Kennesrin. In addition to these works he also wrote on astronomical subjects (Brit. Mus. Add. 14538), and composed a treatise on the astronomical instrument known as the astrolabe, which has been edited and published by F. Nau (Paris, 1899)." Severus' treatise was translated by Jessie Payne Smith Margoliouth in R.T. Gunther, _Astrolabes of the World_, Oxford, 1932, pp. 82–103. * ^ Savage-Smith, Emilie (1993). "Book Reviews". _Journal of Islamic Studies_. 4 (2): 296–299. doi :10.1093/jis/4.2.296 . There is no evidence for the Hellenistic origin of the spherical astrolabe, but rather evidence so far available suggests that it may have been an early but distinctly Islamic development with no Greek antecedents.
* ^ In the Islamic world, it was used to navigate deserts, then
oceans, and to calculate the direction to
* Evans, James (1998), _The History and Practice of Ancient
Astronomy_, Oxford University Press, ISBN 0-19-509539-1 .
* Gunella, Alessandro; Lamprey, John (2007), _Stoeffler's Elucidatio
(translation of Elucidatio fabricae ususque astrolabii into English)_,
* King, D. A (1981), "The Origin of the