Lens and source redshift planes used to construct our past light-cones. These are obtained by stacking half boxes, each |$252.5 \ h^{-1 }\, {Mpc}$| thick, from the observer out to |$z$|_max ∼ 3.0. The lens planes lie at the centre of the projected volumes, and the ‘natural’ source planes correspond to the back of each half box.