title: Issue with astropy conesearch in the SDSS DR8 for specific object
body: <p>I need to search this specific catalog for objects near this coordinate. I am trying to code it because not only do I have this object, but I have many others.</p>
  
  <p>Seting it up:</p>
  
  <pre><code>&gt;&gt;&gt; from astropy.vo.client import conesearch
  &gt;&gt;&gt; from astropy.coordinates import SkyCoord
  &gt;&gt;&gt; from astropy import units as u
  &gt;&gt;&gt; db = 'SDSS DR8 - Sloan Digital Sky Survey Data Release 8 2'
  &gt;&gt;&gt; search_size = 1*u.deg
  &gt;&gt;&gt; c = SkyCoord(ra = 305.008942, dec = -0.975747, unit=u.deg)
  </code></pre>
  
  <p>Running it:</p>
  
  <pre><code>&gt;&gt;&gt; conesearch.conesearch(c, search_size, catalog_db=db)
  Trying http://wfaudata.roe.ac.uk/sdssdr8-dsa/DirectCone?DSACAT=SDSS_DR8&amp;DSATAB=SpecObjAll&amp;
  Downloading http://wfaudata.roe.ac.uk/sdssdr8-dsa/DirectCone?DSACAT=SDSS_DR8&amp;DSATAB=SpeDownloading http://wfaudata.roe.ac.uk/sdssdr8-dsa/DirectCone?DSACAT=SDSS_DR8&amp;DSATAB=SpecObjAll&amp;SR=1.0&amp;DEC=-0.975747&amp;RA=305.008942&amp;VERB=1 [Done]
  WARNING: W50: http://wfaudata.roe.ac.uk/sdssdr8-dsa/DirectCone?DSACAT=SDSS_DR8&amp;DSATAB=SpecObjAll&amp;SR=1.0&amp;DEC=-0.975747&amp;RA=305.008942&amp;VERB=1:51:0: W50: Invalid unit string 'days' [astropy.io.votable.exceptions]
  WARNING: W50: http://wfaudata.roe.ac.uk/sdssdr8-dsa/DirectCone?DSACAT=SDSS_DR8&amp;DSATAB=SpecObjAll&amp;SR=1.0&amp;DEC=-0.975747&amp;RA=305.008942&amp;VERB=1:237:0: W50: Invalid unit string 'Angstroms' [astropy.io.votable.exceptions]
  WARNING: W50: http://wfaudata.roe.ac.uk/sdssdr8-dsa/DirectCone?DSACAT=SDSS_DR8&amp;DSATAB=SpecObjAll&amp;SR=1.0&amp;DEC=-0.975747&amp;RA=305.008942&amp;VERB=1:240:0: W50: Invalid unit string 'Angstroms' [astropy.io.votable.exceptions]
  WARNING: W50: http://wfaudata.roe.ac.uk/sdssdr8-dsa/DirectCone?DSACAT=SDSS_DR8&amp;DSATAB=SpecObjAll&amp;SR=1.0&amp;DEC=-0.975747&amp;RA=305.008942&amp;VERB=1:345:0: W50: Invalid unit string 'nanomaggies' [astropy.io.votable.exceptions]
  WARNING: W50: http://wfaudata.roe.ac.uk/sdssdr8-dsa/DirectCone?DSACAT=SDSS_DR8&amp;DSATAB=SpecObjAll&amp;SR=1.0&amp;DEC=-0.975747&amp;RA=305.008942&amp;VERB=1:348:0: W50: Invalid unit string 'nanomaggies' [astropy.io.votable.exceptions]
  WARNING: W50: http://wfaudata.roe.ac.uk/sdssdr8-dsa/DirectCone?DSACAT=SDSS_DR8&amp;DSATAB=SpecObjAll&amp;SR=1.0&amp;DEC=-0.975747&amp;RA=305.008942&amp;VERB=1:351:0: W50: Invalid unit string 'nanomaggies' [astropy.io.votable.exceptions]
  WARNING: W50: http://wfaudata.roe.ac.uk/sdssdr8-dsa/DirectCone?DSACAT=SDSS_DR8&amp;DSATAB=SpecObjAll&amp;SR=1.0&amp;DEC=-0.975747&amp;RA=305.008942&amp;VERB=1:354:0: W50: Invalid unit string 'nanomaggies' [astropy.io.votable.exceptions]
  WARNING: W50: http://wfaudata.roe.ac.uk/sdssdr8-dsa/DirectCone?DSACAT=SDSS_DR8&amp;DSATAB=SpecObjAll&amp;SR=1.0&amp;DEC=-0.975747&amp;RA=305.008942&amp;VERB=1:357:0: W50: Invalid unit string 'nanomaggies' [astropy.io.votable.exceptions]
  WARNING: W50: http://wfaudata.roe.ac.uk/sdssdr8-dsa/DirectCone?DSACAT=SDSS_DR8&amp;DSATAB=SpecObjAll&amp;SR=1.0&amp;DEC=-0.975747&amp;RA=305.008942&amp;VERB=1:360:0: W50: Invalid unit string 'nanomaggies' [astropy.io.votable.exceptions]
  WARNING: W50: http://wfaudata.roe.ac.uk/sdssdr8-dsa/DirectCone?DSACAT=SDSS_DR8&amp;DSATAB=SpecObjAll&amp;SR=1.0&amp;DEC=-0.975747&amp;RA=305.008942&amp;VERB=1:363:0: W50: Invalid unit string 'nanomaggies' (suppressing further warnings of this type...) [astropy.io.votable.exceptions]
  WARNING: W06: http://wfaudata.roe.ac.uk/sdssdr8-dsa/DirectCone?DSACAT=SDSS_DR8&amp;DSATAB=SpecObjAll&amp;SR=1.0&amp;DEC=-0.975747&amp;RA=305.008942&amp;VERB=1:462:0: W06: Invalid UCD 'IMAGE?': UCD has invalid character '?' in 'IMAGE?' [astropy.io.votable.exceptions]
  WARNING: W25: ?:?:?: W25: 'http://wfaudata.roe.ac.uk/sdssdr8-dsa/DirectCone?DSACAT=SDSS_DR8&amp;DSATAB=SpecObjAll&amp;' failed with: Catalog server 'http://wfaudata.roe.ac.uk/sdssdr8-dsa/DirectCone?DSACAT=SDSS_DR8&amp;DSATAB=SpecObjAll&amp;' returned 0 result [astropy.io.votable.exceptions]
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
    File "/usr/local/lib/python2.7/site-packages/astropy/vo/client/conesearch.py", line 191, in conesearch
      kwargs=args, **kwargs)
    File "/usr/local/lib/python2.7/site-packages/astropy/vo/client/vos_catalog.py", line 877, in call_vo_service
      raise VOSError(err_msg)
  astropy.vo.client.exceptions.VOSError: None of the available catalogs returned valid results.
  </code></pre>
  
  <p>I know that the WARNINGS are just odd issues with the way SDSS set up their search, and it should not effect anything. I have tried up to 20 degrees and still can't find anything. This is just wrong, because I have other objects that are with in 20 degrees and they find objects!</p>