def calc_det_dzb(theta):
    """Calculate detector vertical offset of the bottom raw

    .. note:: formula taken from Table 2 on pag. 68 of CE document
              vol. 3 (Olivier Proux et al.), theta in deg

    """
    return -677.96 + 19.121 * theta - 0.17315 * theta ** 2 + 0.00049335 * theta ** 3