Observed number counts of PN as function of magnitude (top panel) and detection completeness of a simulated PN population (bottom panel). The dashed horizontal line denotes the 50% recovery limit that results in the limiting magnitude m_5007,lim,cat = 29.3 indicated by the dashed vertical line. The solid vertical line denotes the conservative limiting magnitude m_5007,lim = 28.8 based on the decrease of the observed PN-number counts.