Figure 3 - available via license: Creative Commons Attribution 4.0 International
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Section of the celestial sphere: on it the objective positions of the stars are identified by means of a system of celestial coordinates called "equatorial".
Citations
The armillary sphere is a model of the celestial sphere born in ancient Greece. It is made up of graduated metal circles that connect the poles and represent the equator, ecliptic, meridians and parallels; at its center a sphere represents the Earth. It is used to solve various astronomical problems and to explain the movements of stars in the sky. This scientific tool is based on projective geometric principles. Since the fifteenth century it has found a place in paintings and frescoes, where it is used as a symbol of knowledge and wisdom, so much so that it is represented alongside famous people.
