A CMB decrement of has been observed by the Ryle Telescope towards the pair of quasars PC1643+4631 A & B at red-shift separated by 100 arc-seconds (Jones et al. (1997)). Assuming a Sunyaev--Zel'dovich effect from a cluster of galaxies, this is indicative of a rich intervening cluster of total mass , although, no X-ray cluster has yet been observed in that direction. This suggests that the object is lying at a red-shift greater than one. The quasars' spectra analysis reveals that they might be originating from a unique source lensed by the distant cluster (Saunders et al. (1997)).
Using our model, we are able to fit those observations and retrieve the S--Z flux decrement as well as the 100 arc-seconds separation. To do so, we have to consider the cluster described in section 5 with an electron temperature of , which corresponds to a rich but rather cool cluster. As we stated in section 5.1, the resulting Rees--Sciama temperature decrement is which is a considerable fraction of the S--Z decrement, here . Fitting those data is of great importance since such a distant lensed-pair has previously never been observed. As the cluster lies at a rather large red-shift, we believe that a model such as ours, computing rigorously both the cluster and the universe evolutions, is needed.