Projection Effects in the Abell Catalogue

We investigate the influence that projection effects have on the completeness of the the Abell cluster catalogue in the context of an ${\mathrm{\Omega }}_0$=1 CDM Universe. We construct a galaxy catalogue and identify clusters using an algorithm that mimics Abell’s method. Over 30% of Richness Class $\ge$1 clusters have been selected despite not meeting the required intrinsic (3D) richness criterion. Velocity dispersions are shown to have been systematically overestimated.