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- Horizon to equatorial coordinates: Az,El to HA,Dec
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- Horizon to equatorial coordinates: Az,El to HA,Dec
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<H2><A NAME="SECTION000312000000000000000"></A><A NAME="____palDh2e_"></A>
<BR>
palDh2e

   palDh2e
-   Horizon to equatorial coordinates: Az,El to HA,Dec

</H2>
      <DL>
<DT><STRONG>Description:</STRONG></DT>
<DD><DL>
<DD>Convert horizon to equatorial coordinates.

</DD>
</DL>
      
<BR>   
   
</DD>
<DT><STRONG>Invocation:</STRONG></DT>
<DD><DL>
<DD><TT>      palDh2e( double az, double el, double phi, double <SPAN CLASS="MATH"><IMG
 WIDTH="13" HEIGHT="18" ALIGN="BOTTOM" BORDER="0"
 SRC="img1.png"
 ALT="$*$"></SPAN> ha, double <SPAN CLASS="MATH"><IMG
 WIDTH="13" HEIGHT="18" ALIGN="BOTTOM" BORDER="0"
 SRC="img1.png"
 ALT="$*$"></SPAN> dec );
   </TT>
      
</DD>
</DL>
      
<BR>

</DD>
<DT><STRONG>Arguments:</STRONG></DT>
<DD>
<BR>      <DL>
<DT><STRONG>
         az = double (Given)
      </STRONG></DT>
<DD>
         Azimuth (radians)
      
      
</DD>
<DT><STRONG>
         el = double (Given)
      </STRONG></DT>
<DD>
         Elevation (radians)
      
      
</DD>
<DT><STRONG>
         phi = double (Given)
      </STRONG></DT>
<DD>
         Observatory latitude (radians)
      
      
</DD>
<DT><STRONG>
         ha = double <SPAN CLASS="MATH"><IMG
 WIDTH="13" HEIGHT="18" ALIGN="BOTTOM" BORDER="0"
 SRC="img1.png"
 ALT="$*$"></SPAN> (Returned)
      </STRONG></DT>
<DD>
         Hour angle (radians)
      
      
</DD>
<DT><STRONG>
         dec = double <SPAN CLASS="MATH"><IMG
 WIDTH="13" HEIGHT="18" ALIGN="BOTTOM" BORDER="0"
 SRC="img1.png"
 ALT="$*$"></SPAN> (Returned)
      </STRONG></DT>
<DD>
         Declination (radians)
      

</DD>
</DL>
      
<BR>   
   
</DD>
<DT><STRONG>Notes:</STRONG></DT>
<DD><UL>
<LI>All the arguments are angles in radians.

<P>
</LI>
<LI>The sign convention for azimuth is north zero, east <SPAN CLASS="MATH"><IMG
 WIDTH="18" HEIGHT="31" ALIGN="MIDDLE" BORDER="0"
 SRC="img2.png"
 ALT="$+$"></SPAN>pi/2.

<P>
</LI>
<LI>HA is returned in the range <SPAN CLASS="MATH"><IMG
 WIDTH="18" HEIGHT="31" ALIGN="MIDDLE" BORDER="0"
 SRC="img2.png"
 ALT="$+$"></SPAN>/-pi.  Declination is returned
           in the range <SPAN CLASS="MATH"><IMG
 WIDTH="18" HEIGHT="31" ALIGN="MIDDLE" BORDER="0"
 SRC="img2.png"
 ALT="$+$"></SPAN>/-pi/2.

<P>
</LI>
<LI>The latitude is (in principle) geodetic.  In critical
           applications, corrections for polar motion should be applied.

<P>
</LI>
<LI>In some applications it will be important to specify the
           correct type of elevation in order to produce the required
           type of HA,Dec.  In particular, it may be important to
           distinguish between the elevation as affected by refraction,
           which will yield the <TT>"</TT>observed<TT>"</TT> HA,Dec, and the elevation
           in vacuo, which will yield the <TT>"</TT>topocentric<TT>"</TT> HA,Dec.  If the
           effects of diurnal aberration can be neglected, the
           topocentric HA,Dec may be used as an approximation to the
           <TT>"</TT>apparent<TT>"</TT> HA,Dec.

<P>
</LI>
<LI>No range checking of arguments is done.

<P>
</LI>
<LI>In applications which involve many such calculations, rather
           than calling the present routine it will be more efficient to
           use inline code, having previously computed fixed terms such
           as sine and cosine of latitude.

</LI>
</UL>
      
<BR>

</DD>
</DL>
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