 light time.

                  'LT+S'     Correct both the position of `spoint' as
                             seen by the observer, and the position
                             of the illumination source as seen by
                             the target, for light time and stellar
                             aberration.

                  'CN'       Converged Newtonian light time
                             correction. In solving the light time
                             equations for `spoint' and 