Update simbad.rst

Added a detailed example on how to format the RA and Dec fields to return values for specific epochs and equinox. Included the link to the SIMBAD query interface help page containing the full list of possible settings.

Author: fpavogt

docs/simbad/simbad.rst

@@ -530,6 +530,14 @@ Continuing from the above example:
 
     ['main_id', 'coordinates']
 
+Specifying the format of the included VOTable fields
+----------------------------------------------------
+
+The output for several of the VOTable fields can be formatted in many different ways described in the help page of the SIMBAD query interface (see Sect. 4.3 of this page: http://simbad.u-strasbg.fr/simbad/sim-help?Page=sim-fscript). As an example, the epoch and equinox for the Right Ascension and Declination can be specified as follows (e.g. epoch of J2017.5 and equinox of 2000):
+
+.. code-block:: python
+
+    >>> customSimbad.add_votable_fields('ra(2;A;ICRS;J2017.5;2000)','dec(2;D;ICRS;2017.5;2000)')
 
 
 Reference/API