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How to calculate terminator coordinates/subsolar point
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If you want to know the terminator (sun-night boundary) position,
:mod:`pyana.cy1orb.terminator` module will help.

.. code-block:: py

        >>> from pyana.cy1orb.terminator import terminator
        >>> from pyana.util.julday import Julday
        >>> pos = terminator(Julday(2009, 1, 29, 0, 0, 0))

Returned value is a list of ndarray.

.. code-block:: py

        >>> posme = terminator_asdegrees(Julday(2009, 1, 29, 0, 0, 0))

will return the ndarray with shape of nSample x 3.
posme[:, 0] is longitude, posme[:, 1] is latitude and posme[:,2] is height (typically very small number).

For subsolar point, similar interface is implemented.

.. code-block:: py

        >>> from pyana.cy1orb.subsolar import subsolar
        >>> from pyana.util.julday import Julday
        >>> pos = subsolar(Julday(2009, 1, 29, 0, 0, 0))
        >>> posme = subsolar(Julday(2009, 1, 29, 0, 0, 0))

Note that the subsolar point is the point, so pos is 3-length ndarray and posme is [longitude, latitude].