Fixed astronomical rings are mounted on a plinth, like armillary spheres, and can be used as sundials. This ring is also often marked with the zodiac signs and twenty-five stars, similar to the astrolabe. Art historian Jessica Stewart writes that in the 17th century, rings such as the above specimen were “used by astronomers to study and make calculations. These pieces of jewelry were considered tokens of knowledge. Inscriptions or zodiac symbols were often used as decorative elements on the bands.” Christopher Cullen, "Joseph Needham on Chinese Astronomy", Past and Present, No. 87 (May, 1980), pp. 39–53 (45) This ring is sometimes engraved with the months on one side and corresponding zodiac signs on the outside; very similar to an astrolabe.

The armillary sphere is commonly used in heraldry and vexillology, being mainly known as a symbol associated with Portugal, the Portuguese Empire and the Portuguese discoveries. 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. Handmade with extra attention to detail, this ring is the perfect gift for a jewelry collector or budding fashionista in your life.The three rings are oriented with respect to the local meridian, the planet's equator, and a celestial object. The instrument itself can be used as a plumb bob to align it with the vertical. The instrument is then rotated until a single light beam passes through two points on the instrument. This fixes the orientation of the instrument in all three axes. Lindberg, David C.; Shank, Michael H. (7 October 2013). The Cambridge History of Science: Volume 2, Medieval Science. Cambridge University Press. p.173. ISBN 978-1-316-02547-5 . Retrieved 15 May 2018. a b Savage-Smith, Emilie (2017). "Of Making Celestial Globes There Seems No End" (PDF). Bulletin of the Scientific Instrument Society. No. 132: 1–9. The armillary sphere was reintroduced in the national arms and in the national Flag of Portugal in 1911.

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 dial is suspended from a cord or chain; the suspension point on the vertical meridian ring can be changed to match the local latitude. The time is read off on the equatorial ring; in the example below, the center bar is twisted until a sunray passes through a small hole and falls on the horizontal equatorial ring. Armillary sphere rings like the ones in the British Museum’s collection and the Swedish Historical Museum (top) serve a more benign purpose. Folded together, the two-part outer hoop and three interior hoops give the illusion of a simple gold band. Slipped off the wearer’s finger, they can fan out into a physical model of celestial longitude and latitude. The Greek astronomer Hipparchus ( c. 190– c. 120 BC) credited Eratosthenes (276–194 BC) as the inventor of the armillary sphere. [11] [12] [13] [14] [15] Names of this device in Greek include ἀστρολάβος astrolabos and κρικωτὴ σφαῖρα krikōtē sphaira "ringed sphere". [16] The English name of this device comes ultimately from the Latin armilla (circle, bracelet), since it has a skeleton made of graduated metal circles linking the poles and representing the equator, the ecliptic, meridians and parallels. Usually a ball representing the Earth or, later, the Sun is placed in its center. It is used to demonstrate the motion of the stars around the Earth. Before the advent of the European telescope in the 17th century, the armillary sphere was the prime instrument of all astronomers in determining celestial positions. Armillary spheres were among the first complex mechanical devices. Their development led to many improvements in techniques and design of all mechanical devices. Renaissance scientists and public figures often had their portraits painted showing them with one hand on an armillary sphere, which represented the zenith of wisdom and knowledge.

Savage-Smith, Emilie (1985), Islamicate Celestial Globes: Their History, Construction, and Use, Smithsonian Institution Press, Washington, D.C. The equinoctial colure G, passing through the north and south poles of the heaven at N and S, and through the equinoctial points Aries and Libra, in the ecliptic. The whole fabric is supported on a pedestal N, and may be elevated or depressed upon the joint O, to any number of degrees from 0 to 90, by means of the arc P, which is fixed in the strong brass arm Q, and slides in the upright piece R, in which is a screw at r, to fix it at any proper elevation.

a b c d Editors of Encyclopædia Britannica. (16 November 2006). " Armillary Sphere." Encyclopædia Britannica. Accessed 14 October 2017. 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.

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.The ecliptic B, which is divided into 12 signs, and each sign into 30 degrees, and also into the months and days of the year; in such a manner, that the degree or point of the ecliptic in which the sun is, on any given day, stands over that day in the circle of months.