  We present the analysis of spatially-resolved spectroscopic observations of
the born-again planetary nebula (PN) A 78 that are used to investigate the
chemistry and physical properties of its three main morphological components,
namely the inner knots, its eye-like structure, and the low surface-brightness
outer nebula. The H-poor chemical abundances of the inner knots confirm the
born-again nature of A 78, with a N/O abundances ratio consistent with the
predictions of very late thermal pulses (VLTP). On the other hand, the high
Ne/O is not expected in VLTP events, which prompts a possible different
evolutionary path may be involving a binary system. The low N/O ratio and He/H
abundances of the outer shell are indicative of a low-mass progenitor, whereas
the chemical abundances of the eye-like structure, which results from the
interaction between the H-poor born-again material and the outer nebula,
evidence their mixture. Unlike previous works, the extinction is found to be
inhomogeneous, being much higher towards the H-poor inner knots, where the
presence of large amounts of C-rich dust has been previously reported.
Dust-rich material seems to diffuse into outer nebular regions, resulting in
zones of enhanced extinction.
