Analemma
Analemma
The analemma allows precise calculations of mean time (the time by which we set our clocks) by accounting for the tilt of the earth's axis. It also marks the solstices and equinoxes. They are typically a figure-eight shape, but sometimes are oval. Read more in this article from the online Washington Post.
Armillary Sphere
Armillary Sphere
Armillary spheres have concentric rings to indicate planetary orbits, the zodiac band of constellations, and terrestrial and celestial measurement circles such as the Tropics of Cancer and Capricorn and the equator. Sometimes they are mounted with an orrery inside. Sometimes they are mounted as garden sundials.
A Ptolemaic armillary sphere has an earth globe at the center, surrounded by celestial circle and zodiac armillary rings, demonstrating the geocentric theory of the universe developed by Ptolemy and others in ancient Greece and Rome.
A Copernican armillary sphere has a sun ball at the center, with planetary and zodiac armillary rings, demonstrating the modern theory of the solar system, first popularized by Nicolaus Copernicus during the Renaissance.
Cartouche
Cartouche
A cartouche is a decorative emblem on a globe or map, generally containing its title, the name and city of the maker, and sometimes the date or other descriptive information.
Celestial Globe
Celestial Globe (Star Globe)
A celestial globe (star globe) is a globe of the stars and constellation. They are mapped onto a sphere to show how they appear in the night sky from the earth, as if the earth were in the center of the sphere. Given this point of view, the constellation figures are rendered differently from those on a star map -- they are usually reversed and drawn as if we were viewing them from the back, from some imaginary point in the cosmos beyond the earth and stars. Celestial globes are often issued in pairs with terrestrial globes on matching stands.
View a transcript and photographs of George Glazer talking with Martha Stewart about celestial globes and charts.
Copernican Armillary Sphere
Copernican
A map or planetary model showing the earth and planets orbiting the sun, demonstrating the modern theory of the solar system first popularized by Nicolaus Copernicus (1473-1543).
Celestial globe gores
Gores
Printed paper map panels with curved sides tapering to a point at each end, making up the surface of a globe. The gores are designed to make a complete three-dimensional map when cut out and adhered to a sphere.
Horizon band
Horizon Band
Circular band of printed paper laminated to wood or metal, wrapping around the equatorial area of a globe, and generally containing calendar or zodiacal information.
Hour Circle
Hour Circle
Small, thin metal circle on the top of a globe, divided into 24 segments and imprinted or engraved with the hours of the day and night. By turning it, one can calculate the time difference between various locations on the globe.
Globe with Full Meridian
Meridian
Circular or semi-circular band, usually metal, arcing around the globe and passing over, or attached to, the poles. A semi-circular meridian is called a half meridian; a complete circle, a full meridian.
Orrery
Orrery
An orrery is a mechanical astronomical demonstration device used to shown the relative sizes and motions of the known planets in the solar system. It is generally operated by clockwork gears, and is comprised of spheres on wire armatures representing the planets (and their moons) that turn at relative representational rates around the central brass or gilt wood sphere representing the sun, above the stand.
An explanation of an American orrery in a 19th Century trade catalog provides a good general working definition of this instrument and its purpose:
"The Orrery is an instrument which shows the proportional size and relative position of the planets, and times of their revolution. An illustration with this machine brings out our vast system of sun, planets, and moon, into perfect and tangible shape, and in so small a compass that the young, even, can comprehend it."
View a transcript and photographs of George Glazer talking with Martha Stewart about orreries and other celestial globes and charts.
19th-century educator holding a planetary model
Planetaria (Planetary Models)
"Planetaria" is a general term for three-dimensional models of the solar system or of the earth, the moon and the sun. The three major types of planetaria are the tellurian (tellurium), the orrery and the armillary sphere.
Planisphere
Planisphere
A Planisphere is a portable device that shows the stars and constellations visible in the night sky at any given date and time. It consists of a paper or cardboard disk within a folder having an oval cutout. The disk is rotated to match up the hour and minute with the day and month on the outer rim, revealing the visible constellations within the cutout area.
View a transcript and photographs of George Glazer talking with Martha Stewart about planispheres and other celestial globes and charts.
Ptolemaic Armillary Sphere
Ptolemaic
A Ptolemaic map or planetary model shows the earth at the center, surrounded by the planets and constellations, demonstrating the geocentric theory of the universe elaborated by the mathematician, astronomer and geographer Ptolemy (Claudius Ptolemaeus, fl. 127-151 AD) and subsequently modified by others. It was not until the Renaissance that the Ptolemaic system was supplanted by the Copernican conception that in fact the earth revolves around the sun.
Tellurian
Tellurian (Tellurium)
A tellurian (also called tellurium) is a mechanical astronomical demonstration device used to show seasons, eclipses and other astronomical phenomena relating to these bodies. It is generally operated by clockwork gears, gears and chains, or string pulleys, and is comprised of a small terrestrial globe turning at the end of a an arm, spherical painted wood representations of the moon and the planet Venus, and a central brass or gilt wood sphere representing the sun above the stand. Often a zodiac scale is affixed to the base. When operated, at relative representational rates, the earth spins once a day and revolves around the sun once a year, the moon revolves around the earth once a month, and Venus revolves around the sun.
An explanation of an American tellurian in a 19th Century trade catalog provides a good general working definition of this instrument and its purpose:
"The Tellurian, or Season-machine, has been prepared to assist the teacher in explaining the phenomena arising from the revolutions of the earth, and its relations to the other heavenly bodies. It illustrates the causes of
1st. Succession of day and night, and their difference in length.
2d. Changes of the seasons.
3d. Changes of the moon.
4th. Solar and lunar eclipses
5th. Philosophy of tides.
6th. Precession of the equinox.
7th. Differences of solar and sidereal time."
Terrestrial Globe
Terrestrial Globe (World Globe)
A terrestrial globe (world globe) is a sphere with a map of the earth.