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Published online by Cambridge University Press: 25 May 2016
We present deep narrow-band CCD images of four PNe obtained with the Palomar 5-m telescope in the light of [N II]λ6584 + Hα and [O III]λ5007. Several previously undetected structures are found, including faint multiple envelope structures. The inclusion of these sources with data for other multiple envelope PNe published in the literature permit an evaluation of the relationship between PNe ‘shells’ and the thermal pulses of the PN nucleus.