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42 lines
1.1 KiB
42 lines
1.1 KiB
13 years ago
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<sect1 id="ai-meridian">
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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 Local Meridian</title>
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<indexterm
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><primary
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>Local Meridian</primary>
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<seealso
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>Hour Angle</seealso
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> <seealso
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>Celestial Sphere</seealso
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> </indexterm>
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<para
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>The Local Meridian 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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> that is perpendicular to the local <link linkend="ai-horizon"
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>Horizon</link
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>. It passes through the North point on the Horizon, through the <link linkend="ai-cpoles"
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>Celestial Pole</link
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>, up to the <link linkend="ai-zenith"
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>Zenith</link
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>, and through the South point on the Horizon. </para
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><para
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>Because it is fixed to the local Horizon, stars will appear to drift past the Local Meridian as the Earth spins. You can use an object's <link linkend="equatorial"
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>Right Ascension</link
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> and the <link linkend="ai-sidereal"
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>Local Sidereal Time</link
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> to determine when it will cross your Local Meridian (see <link linkend="ai-hourangle"
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>Hour Angle</link
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>). </para>
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</sect1>
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