around eleven of the targets. It is useful to consider whether the non-detections are significant, particularly for RP sources classified as “possible" PNe. In most cases the non-detections can be attributed either to very brief exposure times of less than a minute (3 objects: RP307, RP1759, RP2180), or to the use of filters that do not include strong nebular emission lines (4 objects: RP232, RP241, RP1443, RP1580). In three other cases, it is possible that the nebular emission is extended, but with a surface brightness that is lower than the detection threshold in the [*HST*]{} image. To explore this possibility, we make use of the nebular diameters from @RP06b, the empirical relation of the decline of average \[\] surface brightness with radius from @Shaw_etal06, and assuming the \[\] $\lambda5007$ flux is comparable in intensity to H$\alpha$. The exposure time calculator for ACS (scaling by the relative efficiency for WFPC2 images where necessary) provides some indication of whether extended emission in the remaining objects might have been detectable, given the above assumptions. In one case, RP218, the average surface brightness would have been far below the detection threshold for WFPC2/F606W. But for two objects we might have expected to detect extended 