Quadrupole moment of the redshift-space CCF for voids in a fiducial cosmology that differs from the truth (ε = 1.053 and q = 1). In red we plot the theoretical prediction calculated using an isotropic template ξ^rr. This fits the data in yellow, measured from a simulation in which both halos and voids have been moved by hand, while deviating significantly from the more realistic data in green, where voids are found in a distorted halo catalogue. As in Fig. 2, for simplicity only the case of voxel voids is shown here, though similar results apply to all void finders and can be found in Appendix B.