<sect2 id="calc-angdist">
<title>Angular Distance module</title>
<indexterm><primary>Tools</primary>
<secondary>Astrocalculator</secondary>
<tertiary>Angular Distance module</tertiary>
</indexterm>

<screenshot>
<screeninfo>
The Angular Distance calculator module
</screeninfo>
<mediaobject>
  <imageobject>
    <imagedata fileref="calc-angdist.png" format="PNG"/>
  </imageobject>
  <textobject>
    <phrase>Angular Distance</phrase>
  </textobject>
</mediaobject>
</screenshot>

<para>
The Angular Distance tool is used to measure the angle between any
two points on the sky.  You simply specify the
<link linkend="equatorial">Equatorial coordinates</link> of the
desired pair of points, and then press the
<guibutton>Compute</guibutton> button to obtain the angle between
the two points.
</para>
<para>
There is also a Batch mode for this module.  In batch mode, you
specify an input filename which contains four numbers per line:
the RA and Dec values for pairs of points.  Alternatively, you can
specify a single value for any of these four coordinates in
the calculator panel (the corresponding values in the input file
should be skipped if they are specified in the calculator).
</para>
<para>
Once you have specified the input filename and an output filename,
simply press the <guibutton>Run</guibutton> button to generate the
output file.
</para>
</sect2>
