Astrolabe is called one of the most ancient astronomical tools. There are several types of this device, but anyway the principle of work of an astrolabe – a stereographic projection.
Astrolabe – one of the first tools by which determined height of the Sun or stars, and on them – point coordinates on the Earth's surface.
As the astrolabe is arranged
In ancient times the astrolabe was called still "spider". It really reminds a spider. Its basis – a circle with a high side in which the disk with the lines of the heavenly sphere and points put in a stereographic projection invests. In the center of a disk, concentric circles – a world pole, the heavenly equator, northern and southern tropics are under construction. The heavenly meridian, parallels and azimuthal circles is designated on a disk. The suspended ring is applied to leveling. "Spider" represents a round lattice with the brightest stars applied on it, a zodiac circle. The zodiac circle has a scale. All details are connected together by an axis.
Height of the Sun decided on the help of a ruler which is called "alidade". Then the observer turned "spider" that the necessary points on an ecliptic and on a small circle which carries the name "almucantarat" coincided. Thanks to this action on outer side of the device the stereographic projection of the sky turned out at present.
Sort from antiquity
The first astrolabe appeared in Ancient Greece. Respectively, its name in the literal translation meaning "the one who takes stars" also came from Ancient Greek language. One of the first detailed descriptions of this tool is provided by Vitruvius in the book about architecture. He enters the name of the inventor – Evdoks, he is Apollonius Pergsky. The tool which invented Evdoks was a drum with the star sky represented on it. During that era there were several types of similar tools, they yet not absolutely resembled astrolabes of later eras. In the more or less modern look this tool was made by Theon. It occurred during our era, in the fourth century. Treatises about this tool belong to the same era. The astrolabe served as the tool for definition of time. From Greece the device got on the East. The Arab scientists used it not only for astronomical, but also for the mathematical purposes. In Western Europe at the time of crusaders the Arab astrolabes were used. Then Europeans began to do such tools. There were also scientific works. One of treatises was written by the great English writer Jeffrey Chaucer.
Basis of bases
In Renaissance the astronomy was extremely popular science. Any educated person had to know this science. In turn, studying an astrolabe was the most important section of astronomy. Tools of that time differed not only in the accuracy, but also refined appearance. To collect tools became good form, fashion. Royal collections which decorate the largest museums of the world now reached our days. One of the most famous masters of that time – Dutch Gualterus Aresnius.