| 21. | From the North Pole or South Pole, all constellations south or north of the celestial equator are circumpolar constellations.
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| 22. | Being almost exactly on the celestial equator the star is visible everywhere in the world except for the North Pole.
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| 23. | This is because the Sun crossed the celestial equator from south to north in Aries more than two millennia ago.
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| 24. | The origin moves along the celestial equator at a speed of 15?per hour, the speed of the Earth's rotation.
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| 25. | Celestial objects near the celestial equator are visible worldwide, but they culminate the highest in the sky in the tropics.
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| 26. | Any star that passes the zenith ( overhead ) is on the celestial equator, the basis of the equatorial coordinate system.
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| 27. | The winter solstice, when the sun is farthest south of the celestial equator, falls on the shortest day of the year.
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| 28. | The Northern Sky or Northern Hemisphere is therefore that half of the celestial sphere that is north of the celestial equator.
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| 29. | The Southern Sky or Southern Hemisphere is therefore that half of the celestial sphere that is south of the celestial equator.
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| 30. | The fundamental plane is formed by projection of the Earth's equator onto the celestial sphere, forming the celestial equator ( blue ).
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