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[Alexandr Korol]

Main elements:

• The meridian — a vertical ring passing through the poles and the zenith
• The horizon — a horizontal ring parallel to the earth’s surface
• The celestial equator — a ring parallel to the earth’s equator
• The ecliptic — an inclined ring, deviated by ~23.5° from the celestial equator (this angle corresponds to the tilt of the earth’s axis). The ecliptic shows the visible path of the Sun and the plane of the planets’ orbits
• The Tropics of Cancer and Capricorn — small circles parallel to the ecliptic, marking the extreme northern and southern points of the Sun’s movement
• The polar circles — small circles marking the boundaries of the polar day and night

Sometimes additional rings for the planets, the moon, and the stars were added.