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How to get equator crossing time
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If you want to know the equator crossing time of Chandrayaan-1,
you can use the module :mod:`pyana.cy1orb.Cy1Orbit`.
The method :meth:`pyana.cy1orb.Cy1Orbit.Cy1Orbit.getDayEqOfOrb()`
support this functionality.

.. code-block:: py

        >>> import pyana.cy1orb.Cy1Orbit
        >>> orb = pyana.cy1orb.Cy1Orbit.Cy1Orbit()
        >>> t0 = orb.getDayEqOfOrb(1000)
        (2454862.0829166998,
         1299.0599999999999,
         -1304.9400000000001,
         0.56999999999999995)

The returned is a tuple, which has Julian day, x, y, and z in the LSE
coordinate system in float.

From v1.14, new method :meth:`pyana.cy1orb.Cy1Orbit.Cy1Orbit.getDayEqOfOrb2` is prepared.
This is the same API except that the first argument is ``datetime.datetime`` instance.

.. code-block:: py

        >>> import pyana.cy1orb.Cy1Orbit
        >>> orb = pyana.cy1orb.Cy1Orbit.Cy1Orbit()
        >>> t0 = orb.getDayEqOfOrb2(1000)
        (datetime.datetime(2009, 1, 30, 13, 59, 24, 2864),
        1299.0599999999999,
        -1304.9400000000001,
        0.56999999999999995)