Finally, I found a planetary nebula that also has some data for the faint halo surrounding it. A lot of planetary nebulas have these but images of them <a href="http://www.spacetelescope.org/images/opo0733d/" rel="nofollow">tend to only show the brightest parts</a> while omitting the halo. (Note that's not a covert criticism, to that particular image. I only linked to it as an example.)

Red: hst_11093_02_wfpc2_f658n_pc_sci Green: hst_11093_02_wfpc2_f656n_pc_sci Blue: hst_11093_02_wfpc2_f502n_pc_sci Halo luminosity: hst_06347_20_wfpc2_f656n_wf_sci