我尝试使用PyVO使用简单的锥形搜索使用USNO目录查询给定位置（Ra，Dec in degrees）。输入参数pyvo.dal.scs.search查询采用的是：查询网址，位置元组，搜索半径和详细程度。
问题出现在查询网址上。根据USNO website，查询网址应采用以下形式：
http://www.nofs.navy.mil/cgi-bin/vo_cone.cgi?CAT=USNO-B1&RA=1.0&DEC=-10.0&SR=0.1&VERB=1
但是如果我输入
http://www.nofs.navy.mil/cgi-bin/vo_cone.cgi?CAT=USNO-B1&
作为查询网址，我得到以下输出：
---------------------------------------------------------------------------
DALFormatError Traceback (most recent call last)
<ipython-input-133-450dcb39a4d8> in <module>()
----> 1 uobjs_0 = vo.dal.scs.search('http://www.nofs.navy.mil/cgi-bin/vo_cone.cgi?CAT=USNO-B1&', (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)
---> 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)
--> 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 """
--> 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:
--> 371 raise query.DALFormatError(e, self.getqueryurl())
372
373 def getqueryurl(self, lax=False):
DALFormatError: BadStatusLine: BadStatusLine
我也试过
http://www.nofs.navy.mil/cgi-bin/vo_cone.cgi?
类似于工作的SDSS查询url;但是，由于目录名称不包含在上述输入参数列表中，因此显然会出现错误。有没有办法可以使用PyVO成功查询USNO目录？