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Complex Armillary Sphere replica (Brian Grieg)

This replica combines two armillary spheres into one, containing models for both the Sun and the Moon.  The annual motion of the Sun along the “ecliptic,” its apparent path around the sky, is inclined to the Earth’s equator by 23.5°.  The motion of the Moon follows a path inclined by 5° to the plane of the ecliptic.  This instrument also demonstrates the precession of the equinoxes.

Armillary spheres, serving diverse purposes, were made in many sizes and designs, with different numbers of rings and various accessories.  For ancient astronomers, a simple armillary sphere represented the fundamental circles of the sky, including the local horizon, the celestial equator, the tropics of Cancer and Capricorn, and the ecliptic (or apparent path of the Sun).  Using such an instrument, with the Earth at the center, one may observe the positions of stars, demonstrate the motion of the Sun, and calculate the position of the Sun, bright stars and Zodiac constellations for any date.  

By the 16th century, the crafting of ever more complex armillary spheres in brass and wood reflected attempts to realize, in material form, a functioning model of the celestial orbs described in astronomical works such as Peurbach’s Theorica nova planetarum.  Such complex instruments blur the boundaries between armillary spheres and orreries.  One may be referred to as an “orbarium” or “planetolabium.”

This replica is based on an instrument created in Amsterdam between 1725-1750 by Leonhard Gerhard Valk and now held in The National Maritime Museum Collection at Greenwich, England (ASTO625).

  1. Horizon system

At the top of this 2-ft tall instrument, four arms support a horizon ring (60 cm diameter).  Diverse scales inscribed on the horizon ring indicate degrees, zodiacal sign, names of the month (Latin), and names of the 12 winds (Latin and Greek).  The horizon ring intersects a vertical meridian ring, numbered in 10° increments north or south of the horizon.

2.  Primary sphere:  Equatorial system

Within the horizon ring lies the primary sphere (24.5 cm diameter), comprised of 8 brass rings.  One of these rings, the celestial equator, is divided into 360°.  Four other rings lie parallel to the celestial equator:  the polar circles and the two tropics.

Two rings of the primary sphere are fixed perpendicular to the celestial equator, including the equinoctial colure, which is marked with a scale of declination (degrees north or south of the celestial equator).  Declination is numbered at every 10° increment from 0° to 90°.  Declination may be measured down to 1° divisions. 

The primary sphere also features a zodiacal band attached to the colure rings.  It is divided into twelve regions, each 30° long, bearing the Latin names and figures of the Zodiac constellations.

3.  Ecliptic system

Within the primary sphere, another movable system of rings is based on the poles of the ecliptic, or path of the Sun.  This system is angled to the equatorial system of the primary sphere, where two short axes indicate the offset north and south ecliptic poles.  The ecliptic system consists of 4 rings which model the motions of the Sun and the Moon.  

One ring, not inscribed, lies in the plane of the ecliptic, to model the motion of the Sun.  Two rings parallel to the ecliptic ring represent circles of latitude, at a given distance north and south of the ecliptic.  

The 4th ring is angled to the ecliptic to model the motion of the Moon.  This Moon ring is inscribed: “Nodus (dragon head) euehens” and “aux.”  An opposite inscription reads:  “Nodus (dragon tail) deuehens” and “Oppositum augis.”

4. Earth

In the center, the Earth appears as a globe, with geographical detail (GLB0246).  The globe is inclined 23.5° to offset (or cancel) the ecliptic system.  As a result, the poles of the Earth always point to the equatorial poles of the primary sphere.  William Dampier’s explorations north of New Guinea are shown as Britannia Nova.  California appears as an island.

5. Base

On the base of the instrument, a compass lies at the center of a 32-point Dutch wind rose.  The outer edge contains the names of winds in two languages.

Galileo's World Exhibition Location

Source: History of Science Collections

Section: Observational Astronomy

Section Number: 6

Object Number: 25

Subject Area(s): Astronomy, Scientific Instruments

Time Period: Ancient to Renaissance

Region(s): Europe

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Exhibit Gallery OERs

Johannes Kepler: Harmony of the Universe

Image of Kepler's Harmonic Law

In the work, Harmony of the Universe, Kepler integrated theoretical astronomy and music, ,showing that the motions of the planets employ the same numerical ratios as the most harmonious scales. Kepler's "harmonic law" still describes how planets and stars and satellites and galaxies revolve around one another in space.

Learn more about Kepler's "harmonic law" and its modern realizations in this learning leaflet.

Related OERs:


The Sundial: An Introduction

Bernardino Baldi, Nova gnomonices

A sundial consists of a gnomon, which casts the Sun's shadow, and a dial on which the shadow indicates the time. Learn more about sundials in this learning leaflet.


The Celestial Globe: An Introduction


The night sky looks like an upside-down bowl set on the horizon, but as it turns around during the night it is easy to think of it as a giant sphere. Think of the stars as bright points of light lying on the inside surface of a giant celestial sphere. This sphere rotates around us once a day. A model of the sky as a celestial globe explains the appearances of the sky with simplicity and elegance. Learn more about celestial globes with this learning leaflet.


Kepler's Cosmic Dance suite

Jonathan A. Annis

For the Galileo’s World exhibition, Jonathan A. Annis, a graduate student in the OU School of Music, worked as co-curator of the Music of the Spheres gallery. In this role he composed a suite for harp, flute (doubling alto flute) and oboe (doubling English horn) entirely comprised of musical themes from Kepler’s Harmonices mundi.  Annis arranged the themes, but they derive from Kepler’s musical description of the harmonic law. In this piece, Kepler’s universe becomes a cosmic dance. Visitors to the Music of the Spheres gallery during the Galileo's World exhibition were able to listen to a short excerpt of the suite on an iPad kiosk.  (Background. Learning Leaflet.)  CC-by-sa-nc.


Coma Berenices Learning Leaflet

Coma Berenices Learning Leaflet

Coma Berenices is the only one of the modern 88 official constellations named after a historical figure. It represents the hair of Berenice, Queen of Egypt (267 221 BCE), who reigned with Ptolemy III Euergetes. Learn more about this in this learning leaflet.


Vincenzo Galilei: Discorso particolare intorno all'unisono

Vincenzo LL

Vincenzo Galilei was among the first music theorists to advocate for a new system of tuning based on performance, instead of the mathematical principles of music set fourth by Pythagoras. Pythagorean music theory bases pitch on the mathematical proportions of dividing a string. Vincenzo's primary problem with this system is that, although it is great for the mathematician and the music theorist, it is impractical for the performer. All music based on this particular system of tuning would inevitably sound out of tune and unpleasant. In this learning leaflet learn about the tuning systems in the late-Renaissance period.


Pythagorean Solids: Five Regular Solids

Pythagorean Solids Learning Leaflet

Can you identify the five regular solids? 

Throughout history the regular solids were studied with keen interest by astronomers, mathematicians, artists, architects and philosophers. The Pythagoreans proved that there are only five regular solids: the cube, triangle, octahedron, dodecahedron, and icosahedron. 


Johann Kepler: Blueprints of the Universe

Kepler-Blueprints Learning Leaflet

Is there a mathematical basis of the universe? 

Johann Kepler's "Mystery of the Universe" is one of the brilliant illustrations in the history of astronomy. Kepler used the five regular Pythagorean solids to refute the major objections to Copernicanism. In this work he demonstrated that vast empty regions lying between the planetary spheres, which were required by Copernicus, were not wasted space. Rather, these gaps perfectly matched, within the limits of observational error, the geometry of the 5 regular Pythagorean solids. 


Astronomy & Music: Introduction to the Duochord

Duochord Learning Leaflet

Can you identify simple musical intervals? 

The ancient Pythagoreans envisioned the heavens as a musical scale, comprised of celestial spheres rotating according to harmonious music. For Robert Fludd, a seventeenth-century physician, the universe was a monochord, its physical structure unintelligible without an understanding of music. In this activity, explore the relationship between mathematics, astronomy, and music.