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35 lines
976 B
35 lines
976 B
13 years ago
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<sect1 id="ai-cequator">
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<sect1info>
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<author
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><firstname
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>Jason</firstname
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> <surname
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>Harris</surname
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> </author>
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</sect1info>
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<title
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>The Celestial Equator</title>
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<indexterm
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><primary
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>Celestial Equator</primary>
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<seealso
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>Equatorial Coordinates</seealso>
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</indexterm>
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<para
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>The <firstterm
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>Celestial Equator</firstterm
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> is an imaginary <link linkend="ai-greatcircle"
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>great circle</link
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> on the <link linkend="ai-csphere"
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>celestial sphere</link
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>. The celestial equator is the fundamental plane of the <link linkend="equatorial"
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>Equatorial Coordinate System</link
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>, so it is defined as the locus of points with Declination of zero degrees. It is also the projection of the Earth's equator onto the sky. </para>
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<para
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>The Celestial Equator and the <link linkend="ai-ecliptic"
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>Ecliptic</link
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> are set at an angle of 23.5 degrees in the sky. The points where they intersect are the Vernal and Autumnal <link linkend="ai-equinox"
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>Equinoxes</link
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>. </para>
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</sect1>
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