In astronomy and navigation, the celestial sphere is an abstract sphere that has an arbitrarily large radius and is concentric to Earth. All objects in...

The celestial spheres, or celestial orbs, were the fundamental entities of the cosmological models developed by Plato, Eudoxus, Aristotle, Ptolemy, Copernicus...

and south celestial poles are the two points in the sky where Earth's axis of rotation, indefinitely extended, intersects the celestial sphere. The north...

northern celestial hemisphere, also called the Northern Sky, is the northern half of the celestial sphere; that is, it lies north of the celestial equator...

different theories about the dynamics of the celestial spheres. They explained the motions of the various nested spheres in terms of the materials of which they...

direction on a celestial sphere, if the object's distance is unknown or trivial. Spherical coordinates, projected on the celestial sphere, are analogous...

armillary sphere (variations are known as spherical astrolabe, armilla, or armil) is a model of objects in the sky (on the celestial sphere), consisting...

The celestial equator is the great circle of the imaginary celestial sphere on the same plane as the equator of Earth. By extension, it is also a plane...

in equilibrium. The Earth is often approximated as a sphere in geography, and the celestial sphere is an important concept in astronomy. Manufactured items...

southern celestial hemisphere, also called the Southern Sky, is the southern half of the celestial sphere; that is, it lies south of the celestial equator...

perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic against...

the celestial sphere visible to the observer, and its projection on the celestial equatorial plane.   The geographic south of the celestial sphere acts...

A globe is a spherical model of Earth, of some other celestial body, or of the celestial sphere. Globes serve purposes similar to maps, but, unlike maps...

positioned at the centre of the celestial sphere, is of the gnomonic projection inside of the celestial sphere, whereas the celestial globe is orthographic projection...

exist attached on a giant celestial sphere, or firmament, which revolves daily around Earth. Hence it was known as the "sphere of fixed stars", which acted...

United Nations, private sponsors and artists. The Celestial Sphere (also known as the Armillary Sphere) in the Ariana Park of the Palais des Nations is...

with mapping stars, galaxies, and other astronomical objects on the celestial sphere. Measuring the position and light of charted objects requires a variety...

around Earth about once per day. The stars appeared to be fixed on a celestial sphere rotating once each day about an axis through the geographic poles of...

upon the celestial sphere. hour circle Any imaginary great circle drawn upon the celestial sphere that passes through both of the celestial poles and...

anti-meridian), and the intersection of the plane with the celestial sphere is the celestial meridian for that location and time. There are several ways...

separating the hemispheres is called the celestial horizon, which is defined as the great circle on the celestial sphere whose plane is normal to the local...

fixed stars on the theoretical celestial sphere. More exactly, sidereal time is the angle, measured along the celestial equator, from the observer's meridian...

aetheric celestial sphere emulates one of the unmoved movers, as best it can, by uniform circular motion. The first heaven, the outmost sphere of fixed...

dec; symbol δ) is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. The...

The zenith (UK: /ˈzɛnɪθ/, US: /ˈziː-/) is the imaginary point on the celestial sphere directly "above" a particular location. "Above" means in the vertical...

astronomy. In antiquity, he was credited with inventing the first celestial sphere. In some texts, he is even credited with the invention of astronomy...

Minkowski spacetime and are modeled by points on the celestial sphere. Then a given point on the celestial sphere can be associated with ξ = u + iv, a complex...

In the field of astronomy, the sky is also called the celestial sphere. This is an abstract sphere, concentric to the Earth, on which the Sun, Moon, planets...

also known as a celestial body or object Celestial coordinate system, a system for mapping positions on the celestial sphere Celestial mechanics, the branch...

orbium coelestium (English translation: On the Revolutions of the Heavenly Spheres) is the seminal work on the heliocentric theory of the astronomer Nicolaus...