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32 lines
1.0 KiB
32 lines
1.0 KiB
15 years ago
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<sect1 id="ai-zenith">
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<sect1info>
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<author>
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<firstname>Jason</firstname>
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<surname>Harris</surname>
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</author>
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</sect1info>
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<title>The Zenith</title>
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<indexterm><primary>Zenith</primary>
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<seealso>Horizontal Coordinates</seealso>
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</indexterm>
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<para>
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The Zenith is the point in the sky where you are looking when you look
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<quote>straight up</quote> from the ground. More precisely, it is the point on
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the sky with an <firstterm>Altitude</firstterm> of +90 Degrees; it is the Pole
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of the <link linkend="horizontal">Horizontal Coordinate
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System</link>. Geometrically, it is the point on the <link
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linkend="ai-csphere">Celestial Sphere</link> intersected by a line drawn from
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the center of the Earth through your location on the Earth's surface.
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</para><para>
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The Zenith is, by definition, a point along the <link
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linkend="ai-meridian">Local Meridian</link>.
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</para>
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<tip>
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<para>Exercise:</para>
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<para>
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You can point to the Zenith by pressing <keycap>Z</keycap> or by selecting
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<guimenuitem>Zenith</guimenuitem> from the <guimenu>Pointing</guimenu> menu.
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</para>
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</tip>
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</sect1>
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