What is an Armillary

                                    Portrait of Wu Yong a character in the Chinese novel Water Margin

An Amillary (Amillary Sphere) is an ancient device which models the heavens.  I consists of a series of concentric rings, some fixed and some moveable.  The center of these rings was a sphere representing center of the universe.  Until the time of Copernicus in the 16^th Century this sphere was an earth globe.  As a result of Conpernicus’ theories an Amillary was developed with the central sphere representing the sun.  Consequently, an Amillary with a central earth sphere is known as Ptolemaic and an Amillary with a central sun sphere is known as Copernican.

Drawing of a mechanically-rotated Armillary from 1092

The origin of the Amillary is unknown but they were widely in use in both Greece and China by the first Century B.C.  By the 8^th Century Persian and Arab astronomers had modified and improved the device.  Korean inventors made additional improvements during the 15^th Century.  An Amillary activated by a clock mechanism was built in Korea in the 17^th Century and still survives today.  Modern technology has made the Armilary obsolete for precise, practical astronomical observations.  Today it is an object of art, a historic model of the celestial universe, a historic mechanical computational device, a training device, and a conversation piece.

                                                                      Botticelli painting of an Armillary from 1480

An Armillary has two exterior bands surrounding the inner cage.  A wide, horizontal band representing the viewer’s horizon is fixed and parallel to the floor.  A vertical rotating ring  represents the meridian or azimuth.  Moving this ring allows the viewer to adjust the latitude.  These rings are engraved with degrees of the compass. 

The basket inside these two rings contains the representation of the earth with its axis running through the poles and attached to the appropriate points on the horizontal exterior band.  The basket’s center ring represents the equator while the two horizontal rings are the Tropic of Cancer (22.5 degrees north of the equator) and the Tropic of Capricorn (22.5 degrees south of the equator).  The wide band surrounding the inner cage represents the path of the sun and other celestial bodies.

Sculpture of Roger Bacon holding an Armillary 

The Armillary represents ancient celestial astronomy.  It was used to make astronomical observations of the heavens.  Modifications were additions to the Armillary for use as a navigational aid.  Viewing tubes were added in order to make more precise measurements.  Prior to the development of the telescope in the 17^th Century, the Armillary was the primary instrument used by astronomers to determine their celestial position.  It has been equipped with mechanical clocks to facilitate movement of the rings for continuous celestial predictions.  It can be thought of as an early analog computer.

Ship Models Online offers a variety of Amillaries shown on its Armillaries and Globes category.  The price for two of these items is discounted during our February sale.