'Parameters
phi_N, theta_N : float (deg) or `~astropy.units.Quantity`
Angles in the Native coordinate system.
lon, lat, lon_pole : float (in deg) or `~astropy.units.Quantity`
Parameter values when the model was initialized.
Returns
alpha_C, delta_C : float (deg) or `~astropy.units.Quantity`
Angles on the Celestial sphere.'

def evaluate(self, phi_N, theta_N, lon, lat, lon_pole):

    if isinstance(lon, u.Quantity):
        lon = lon.value
        lat = lat.value
        lon_pole = lon_pole.value
    phi = (lon_pole - (np.pi / 2))
    theta = (- ((np.pi / 2) - lat))
    psi = (- ((np.pi / 2) + lon))
    (alpha_C, delta_C) = super(RotateNative2Celestial, self)._evaluate(phi_N, theta_N, phi, theta, psi)
    return (alpha_C, delta_C)
