def illuminant_scotopic_luminance(L_A, CCT):
    """
    Returns the approximate scotopic luminance :math:`L_{AS}` of the
    illuminant.

    Parameters
    ----------
    L_A : numeric
        Adapting field *luminance* :math:`L_A` in :math:`cd/m^2`.
    CCT : numeric
        Correlated color temperature :math:`T_{cp}` of the illuminant.

    Returns
    -------
    numeric
        Approximate scotopic luminance :math:`L_{AS}`.

    Examples
    --------
    >>> illuminant_scotopic_luminance(318.31, 6504.0)  # doctest: +ELLIPSIS
    769.9376286...
    """

    CCT = 2.26 * L_A * ((CCT / 4000) - 0.4) ** (1 / 3)
    return CCT