kstars/doc/calc-apcoords.docbook

0001 <sect2 id="calc-apcoords">
0002 <title>Apparent Coordinates module</title>
0003 <indexterm><primary>Tools</primary>
0004 <secondary>Astrocalculator</secondary>
0005 <tertiary>Apparent Coordinates module</tertiary>
0006 </indexterm>
0007
0008 <screenshot>
0009 <screeninfo>
0010 The Apparent Coordinates calculator module
0011 </screeninfo>
0012 <mediaobject>
0013   <imageobject>
0014     <imagedata fileref="calc-apcoords.png" format="PNG"/>
0015   </imageobject>
0016   <textobject>
0017     <phrase>Apparent Coordinates</phrase>
0018   </textobject>
0019 </mediaobject>
0020 </screenshot>
0021
0022 <para>
0023 The Apparent Coordinates module converts the <firstterm>catalog
0024 coordinates</firstterm> of a point in the sky to its
0025 <firstterm>apparent coordinates</firstterm> for any date.  The
0026 coordinates of objects in the sky are not fixed, because of
0027 <link linkend="ai-precession">precession</link>, nutation and
0028 aberration.  This module takes these effects into account.
0029 </para>
0030 <para>
0031 To use the module, first enter the desired target date and time
0032 in the <guilabel>Target Time &amp; Date</guilabel> section.  Then,
0033 enter the catalog coordinates in the <guilabel>Catalog
0034 Coordinates</guilabel> section.  Alternatively you can set the
0035 catalog coordinates by selecting an object using the <guilabel>Find Object</guilabel>
0036 dialog.  You can also specify the
0037 catalog's epoch here (usually 2000.0 for modern object
0038 catalogs).  Then the object's coordinates for the target date
0039 will be displayed in the <guilabel>Apparent coordinates:</guilabel>
0040 section.
0041 </para>
0042 </sect2>