title: How do I query USNO catalogs using PyVO?
body: <p>I'm trying to use PyVO to query a given position (Ra,Dec in degrees) with USNO catalog using a simple cone search. The input parameters <code>pyvo.dal.scs.search</code> query takes are: query url, postion tuple, radius of search and verbosity.</p>
  
  <p>The problem arises with the query url. Based on the USNO <a href="http://www.nofs.navy.mil/data/fchpix/vo_nofs.html" rel="nofollow noreferrer" title="website">website</a>, the query url should be of the form of:</p>
  
  <pre><code>http://www.nofs.navy.mil/cgi-bin/vo_cone.cgi?CAT=USNO-B1&amp;RA=1.0&amp;DEC=-10.0&amp;SR=0.1&amp;VERB=1
  </code></pre>
  
  <p>However if I input</p>
  
  <pre><code>http://www.nofs.navy.mil/cgi-bin/vo_cone.cgi?CAT=USNO-B1&amp;
  </code></pre>
  
  <p>as the query url, I get the following output:</p>
  
  <pre><code>---------------------------------------------------------------------------
  DALFormatError                            Traceback (most recent call last)
  &lt;ipython-input-133-450dcb39a4d8&gt; in &lt;module&gt;()
  ----&gt; 1 uobjs_0 = vo.dal.scs.search('http://www.nofs.navy.mil/cgi-bin/vo_cone.cgi?CAT=USNO-B1&amp;', (ra[0],dec[0]), 0.25)
  
  /usr/local/lib/python2.7/dist-packages/pyvo-0.4.1-py2.7.egg/pyvo/dal/scs.pyc in search(url, pos, radius, verbosity)
       73     """
       74     service = SCSService(url)
  ---&gt; 75     return service.search(pos, radius, verbosity)
       76 
       77 class SCSService(query.DALService):
  
  /usr/local/lib/python2.7/dist-packages/pyvo-0.4.1-py2.7.egg/pyvo/dal/scs.pyc in search(self, pos, radius, verbosity)
      134         """
      135         q = self.create_query(pos, radius, verbosity)
  --&gt; 136         return q.execute()
      137 
      138     def create_query(self, pos=None, radius=None, verbosity=None):
  
  /usr/local/lib/python2.7/dist-packages/pyvo-0.4.1-py2.7.egg/pyvo/dal/scs.pyc in execute(self)
      341         pyvo.dal.query.DALQueryError
      342         """
  --&gt; 343         return SCSResults(self.execute_votable(), self.getqueryurl(True))
      344 
      345     def execute_votable(self):
  
  /usr/local/lib/python2.7/dist-packages/pyvo-0.4.1-py2.7.egg/pyvo/dal/scs.pyc in execute_votable(self)
      369                                        "deprecated DEFINITIONS element")
      370         except Exception as e:
  --&gt; 371             raise query.DALFormatError(e, self.getqueryurl())
      372 
      373     def getqueryurl(self, lax=False):
  
  DALFormatError: BadStatusLine: BadStatusLine
  </code></pre>
  
  <p>I also tried </p>
  
  <pre><code>http://www.nofs.navy.mil/cgi-bin/vo_cone.cgi?
  </code></pre>
  
  <p>which is similar to the working SDSS query url; however I get an error obviously as catalog name isn't included in the list of the input parameters mentioned above. Is there a way I can successfully query USNO catalogs using PyVO?</p>