Point-source test left column: colour-selected PNe; right column: simulated PN-population. Top row: m_n − m_core vs. m_n, the black lines indicate the region in which 95% of the simulated population fall. Bottom row: R_h as a function of m_n. We impose a limit of 3.5 pixel on R_h, such that 95% of the simulated population is included. Objects which satisfy both criteria are plotted in red and are termed point-like.