Simbad query_region() fails when radius is set to small values.

[rickyegeland]

Example:

>>> result = astroquery.simbad.Simbad.query_region(coord.ICRS("00h00m0.0s 00h00m0.0s"), radius=1.0 * u.marcsec, equinox=2000.
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/egeland/Code/sunstardb/lib/python2.7/site-packages/astroquery-0.2.dev1928-py2.7.egg/astroquery/simbad/core.py", line 440, in query_region
    equinox=equinox, epoch=epoch)
  File "/Users/egeland/Code/sunstardb/lib/python2.7/site-packages/astroquery-0.2.dev1928-py2.7.egg/astroquery/simbad/core.py", line 470, in query_region_async
    caller='query_region_async')
  File "/Users/egeland/Code/sunstardb/lib/python2.7/site-packages/astroquery-0.2.dev1928-py2.7.egg/astroquery/simbad/core.py", line 44, in wrapper
    return func(*args, **kwargs)
  File "/Users/egeland/Code/sunstardb/lib/python2.7/site-packages/astroquery-0.2.dev1928-py2.7.egg/astroquery/simbad/core.py", line 60, in wrapper
    return func(*args, **kwargs)
  File "/Users/egeland/Code/sunstardb/lib/python2.7/site-packages/astroquery-0.2.dev1928-py2.7.egg/astroquery/simbad/core.py", line 681, in _args_to_payload
    kwargs['radius'] = _parse_radius(kwargs['radius'])
  File "/Users/egeland/Code/sunstardb/lib/python2.7/site-packages/astroquery-0.2.dev1928-py2.7.egg/astroquery/simbad/core.py", line 765, in _parse_radius
    index = min([i for (i,val) in enumerate(angle.dms) if int(val) > 0])
ValueError: min() arg is an empty sequence
>>> result = astroquery.simbad.Simbad.query_region(coord.ICRS("00h00m0.0s 00h00m0.0s"), radius=1.0 * u.marcsec, equinox=2000.0, epoch='J2000')

I was deliberately trying to make a query that returns no results, in order to make a test case. It seems something falls apart in this case. u is astropy.units.

[keflavich]

Ah... interesting. angle.dms is being set to a value <1 so this code ends up trying to take min([]), i.e. min of an empty list. I guess we should check for that. I wonder what SIMBAD's minimum radius is...

[cdeil]

@rickyegeland Do you have the time / motivation to implement a fix and add a test for this?
:-)

[rickyegeland]

OK, I'll take a look next week.