<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 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 a number of parameters (up to four) on each line: 
the initial right ascension (RA), initial declination (Dec), final right ascension and 
final declination. By default, each line should contain four numbers signifying 
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>