def get_AV_infinity(ra,dec,frame='icrs'):
    """
    Gets the A_V exctinction at infinity for a given line of sight.

    Queries the NED database using ``curl``.

    .. note::

        It would be desirable to rewrite this to avoid dependence
        on ``curl``.

    :param ra,dec:
        Desired coordinates, in degrees.

    :param frame: (optional)
        Frame of input coordinates (e.g., ``'icrs', 'galactic'``)
    """
    coords = SkyCoord(ra,dec,unit='deg',frame=frame).transform_to('icrs')

    rah,ram,ras = coords.ra.hms
    decd,decm,decs = coords.dec.dms
    if decd > 0:
        decsign = '%2B'
    else:
        decsign = '%2D'
    url = 'http://ned.ipac.caltech.edu/cgi-bin/nph-calc?in_csys=Equatorial&in_equinox=J2000.0&obs_epoch=2010&lon='+'%i' % rah + \
        '%3A'+'%i' % ram + '%3A' + '%05.2f' % ras + '&lat=%s' % decsign + '%i' % abs(decd) + '%3A' + '%i' % abs(decm) + '%3A' + '%05.2f' % abs(decs) + \
        '&pa=0.0&out_csys=Equatorial&out_equinox=J2000.0'

    tmpfile = '/tmp/nedsearch%s%s.html' % (ra,dec)
    cmd = 'curl -s \'%s\' -o %s' % (url,tmpfile)
    sp.Popen(cmd,shell=True).wait()
    AV = None
    with open(tmpfile, 'r') as f:
        for line in f:
            m = re.search('V \(0.54\)\s+(\S+)',line)
            if m:
                AV = float(m.group(1))
    if AV is None:
        logging.warning('Error accessing NED, url={}'.format(url))
        with open(tmpfile) as f:
            for line in f:
                logging.warning(line)



    os.remove(tmpfile)
    return AV
Gets the A_V exctinction at infinity for a given line of sight.

    Queries the NED database using ``curl``.

    .. note::

        It would be desirable to rewrite this to avoid dependence
        on ``curl``.

    :param ra,dec:
        Desired coordinates, in degrees.

    :param frame: (optional)
        Frame of input coordinates (e.g., ``'icrs', 'galactic'``)