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The declination ring is moveable, and rotates on pivots set in the meridian ring. An imaginary line connecting these pivots is parallel to the Earth's axis. The declination "ring" of the traveller's sundial above is not a ring at all, but an oblong loop with a slider for setting the season. When the shadow of the rings are aligned so that they appear to be in the same, or nearly the same, place, the meridian identifies itself. [ clarification needed] Meridional ring [ edit ] The altitude of the sun does not change much in a single day at the poles (where the sun rises and sets once a year), so rough measurements of solar altitude don't vary with time of day at high latitudes. The armillary sphere was reintroduced in the national arms and in the national Flag of Portugal in 1911. Often equipped with a graduated scale, it can be used to measure right ascension. On the traveller's sundial shown above, it is the inner ring.

Further information: Planetarium and Antikythera mechanism Ptolemy with an armillary sphere model, by Joos van Ghent and Pedro Berruguete, 1476, Louvre, Paris The equatorial ring occupies a plane parallel to the celestial equator, at right angles to the meridian. It is aligned by And so, by this construction, the machine is equally fitted to show either the real motion of the earth, or the apparent motion of the heavens.The armillary sphere survives as useful for teaching, and may be described as a skeleton celestial globe, the series of rings representing the great circles of the heavens, and revolving on an axis within a horizon. With the earth as center such a sphere is known as Ptolemaic; with the sun as center, as Copernican. [1] In the 17th century, it became associated with the Portuguese dominion of Brazil. In 1815, when Brazil gained the status of kingdom united with that of Portugal, its coat of arms was formalized as a golden armillary sphere in a blue field. Representing Brazil, the armillary sphere became also present in the arms and the flag of the United Kingdom of Portugal, Brazil and the Algarves. When Brazil became independent as an empire in 1822, the armillary sphere continued to be present in its national arms and in its national flag. The celestial sphere of the present Flag of Brazil replaced the armillary sphere in 1889. 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, 1839, OCLC 165707441 (or id. Rheinisches Museum für Philologie 6 (1839): 127–71); repr. and translated into French by Alain Philippe Segonds, Jean Philopon, traité de l'astrolabe, Paris: Librairie Alain Brieux, 1981, OCLC 10467740; and translated into English by H.W. Green in R.T. Gunther, The Astrolabes of the World, Vol. 1/2, Oxford, 1932, OL 18840299M repr. London: Holland Press, 1976, OL 14132393M pp. 61–81.

Elements of the general description incorporate text from the Encyclopædia Britannica First Edition (1771).

Used by astronomers to study and make calculations, these pieces of jewelry were considered tokens of knowledge.

Savage-Smith, Emilie (1985), Islamicate Celestial Globes: Their History, Construction, and Use, Smithsonian Institution Press, Washington, D.C. The flag of Portugal features an armillary sphere. The armillary sphere is also featured in Portuguese heraldry, associated with the Portuguese discoveries during the Age of Exploration. Manuel I of Portugal, for example, took it as one of his symbols where it appeared on his standard, and on early Chinese export ceramics made for the Portuguese court. In the flag of the Empire of Brazil, the armillary sphere is also featured. The British Museum has a collection of several armillary sphere rings that are incredibly well-crafted and detailed. When closed, they look like any other ring, but as the different bands are fanned out, the rings take on a unique quality. Built with anywhere between two to eight moving bands, these intricate pieces of jewelry would need to have been executed by skilled craftsmen.

The Arctic Circle E, and the Antarctic Circle F, each 23 1⁄ 2 degrees from its respective pole at N and S. Kern, Ralf: Wissenschaftliche Instrumente in ihrer Zeit. Vom 15. – 19. Jahrhundert. Verlag der Buchhandlung Walther König 2010, ISBN 978-3-86560-772-0

Further advances in this instrument were made by Danish astronomer Tycho Brahe (1546–1601), who constructed three large armillary spheres which he used for highly precise measurements of the positions of the stars and planets. They were described in his Astronomiae Instauratae Mechanica. [25]