George Abell's examination of the Palomar Observatory Sky Survey in the mid 1960's yielded 86 planetary nebulae which have proven to be an observer's dream challenge, for many of these celestial objects are not only very faint in magnitude even under very dark skies but are also relatively large with dimensions often measured in minutes in lieu of seconds. Later analysis of Abell's catalog revealed that at least four of these objects, namely Abell 11, 32, 76 and 85, are not planetary nebulae at all. For the avid observer, an O-III filter is highly recommended in order to have any hope of visually detecting these elusive wonders.

An even greater number of planetary nebula can be found within the NGC and IC catalogs and are available elsewhere on this site (see here). As is evident from the images below, planetary nebulae are beautiful to look at thanks to the glowing and colourful gaseous shrouds which make their planetary appearance and colouration possible as a result of stars having exhausted their nuclear material and having reached the last stages of their life. Some of the more exotic planetary nebulae include the Cat's Eye (NGC 6543), the Saturn Nebula (NGC 7009), the Ghost of Jupiter (NGC 3242) and the Owl Nebula (M97).

Note: Three excellent references are the associated articles in S&T (May/2002) and Astronomy Magazine (Feb/2005, June/2011).