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42 lines
1.4 KiB
42 lines
1.4 KiB
15 years ago
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<sect2 id="calc-apcoords">
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<title>Apparent Coordinates module</title>
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<indexterm><primary>Tools</primary>
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<secondary>Astrocalculator</secondary>
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<tertiary>Apparent Coordinates module</tertiary>
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</indexterm>
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<screenshot>
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<screeninfo>
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The Apparent Coordinates calculator module
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</screeninfo>
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<mediaobject>
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<imageobject>
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<imagedata fileref="calc-apcoords.png" format="PNG"/>
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</imageobject>
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<textobject>
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<phrase>Apparent Coordinates</phrase>
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</textobject>
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</mediaobject>
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</screenshot>
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<para>
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The Apparent Coordinates module converts the <firstterm>catalog
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coordinates</firstterm> of a point in the sky to its
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<firstterm>apparent coordinates</firstterm> for any date. The
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coordinates of objects in the sky are not fixed, because of
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<link linkend="ai-precession">precession</link>, nutation and
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aberration. This module takes these effects into account.
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</para>
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<para>
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To use the module, first enter the desired target date and time
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in the <guilabel>Target Time/Date</guilabel> section. Then,
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enter the catalog coordinates in the <guilabel>Catalog
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Coordinates</guilabel> section. You can also specify the
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catalog's epoch here (usually 2000.0 for modern object
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catalogs). Finally, press the <guibutton>Compute</guibutton>
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button, and the object's coordinates for the target date
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will be displayed in the <guilabel>Apparent Coordinates</guilabel>
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section.
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</para>
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</sect2>
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