<sect2 id="calc-precess"> <title >Precession module</title> <indexterm ><primary >Tools</primary> <secondary >Astrocalculator</secondary> <tertiary >Precession module</tertiary> </indexterm> <screenshot> <screeninfo >The Precession calculator module </screeninfo> <mediaobject> <imageobject> <imagedata fileref="calc-precess.png" format="PNG"/> </imageobject> <textobject> <phrase >Precession</phrase> </textobject> </mediaobject> </screenshot> <para >This module is similar to the <link linkend="calc-apcoords" >Apparent Coordinates module</link >, but it only applies the effect of <link linkend="ai-precession" >precession</link >, not of nutation or aberration. </para> <para >To use the module, first enter the input coordinates and their epoch in the <guilabel >Original Coordinates</guilabel > section. You must also fill in the target epoch in the <guilabel >Precessed Coordinates</guilabel > section. Then, press the <guibutton >Compute</guibutton > button, and the object's coordinates, precessed to the target Epoch, are presented in the <guilabel >Precessed Coordinates</guilabel > section. </para> </sect2>