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45 lines
1.1 KiB
45 lines
1.1 KiB
13 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
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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 Zenith</title>
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<indexterm
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><primary
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>Zenith</primary>
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<seealso
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>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 <quote
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>straight up</quote
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> from the ground. More precisely, it is the point on the sky with an <firstterm
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>Altitude</firstterm
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> of +90 Degrees; it is the Pole of the <link linkend="horizontal"
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>Horizontal Coordinate System</link
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>. Geometrically, it is the point on the <link linkend="ai-csphere"
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>Celestial Sphere</link
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> intersected by a line drawn from the centre of the Earth through your location on the Earth's surface. </para
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><para
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>The Zenith is, by definition, a point along the <link linkend="ai-meridian"
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>Local Meridian</link
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>. </para>
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<tip>
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<para
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>Exercise:</para>
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<para
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>You can point to the Zenith by pressing <keycap
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>Z</keycap
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> or by selecting <guimenuitem
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>Zenith</guimenuitem
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> from the <guimenu
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>Location</guimenu
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> menu. </para>
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</tip>
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</sect1>
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