.. _Skyfield: http://rhodesmill.org/skyfield/
.. _PyEphem: http://rhodesmill.org/pyephem/
.. _Numpy: http://www.numpy.org
.. _Matplotlib: http://www.matplotlib.org
.. _pytz: https://pypi.python.org/pypi/pytz/
.. _pytest-mpl: https://pypi.python.org/pypi/pytest-mpl
.. _astroquery: https://astroquery.readthedocs.io
.. _pytest-astropy: https://github.com/astropy/pytest-astropy
