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+<sect1 id="ai-cequator">
+<sect1info>
+<author>
+<firstname>Jason</firstname>
+<surname>Harris</surname>
+</author>
+</sect1info>
+<title>The Celestial Equator</title>
+<indexterm><primary>Celestial Equator</primary>
+<seealso>Equatorial Coordinates</seealso>
+</indexterm>
+<para>
+The <firstterm>Celestial Equator</firstterm> is an imaginary <link
+linkend="ai-greatcircle">great circle</link> on the <link
+linkend="ai-csphere">celestial sphere</link>. The celestial equator
+is the fundamental plane of the <link linkend="equatorial">Equatorial
+Coordinate System</link>, 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>
+<para>
+The Celestial Equator and the <link linkend="ai-ecliptic">Ecliptic</link>
+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">Equinoxes</link>.
+</para>
+</sect1>