kstars/doc/cequator.docbook

0001 <sect1 id="ai-cequator">
0002 <sect1info>
0003 <author>
0004 <firstname>Jason</firstname>
0005 <surname>Harris</surname>
0006 </author>
0007 </sect1info>
0008 <title>The Celestial Equator</title>
0009 <indexterm><primary>Celestial Equator</primary>
0010 <seealso>Equatorial Coordinates</seealso>
0011 </indexterm>
0012 <para>
0013 The <firstterm>Celestial Equator</firstterm> is an imaginary <link
0014 linkend="ai-greatcircle">great circle</link> on the <link
0015 linkend="ai-csphere">celestial sphere</link>.  The celestial equator
0016 is the fundamental plane of the <link linkend="equatorial">Equatorial
0017 Coordinate System</link>, so it is defined as the locus of points
0018 with Declination of zero degrees.  It is also the projection of the
0019 Earth's equator onto the sky.
0020 </para>
0021 <para>
0022 The Celestial Equator and the <link linkend="ai-ecliptic">Ecliptic</link>
0023 are set at an angle of 23.5 degrees in the sky.  The points where they
0024 intersect are the Vernal and Autumnal <link
0025 linkend="ai-equinox">Equinoxes</link>.
0026 </para>
0027 </sect1>