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Published online by Cambridge University Press: 26 May 2016
Abell 30 is one of a small number of PN known as born-again PN, which appear to be old nebulae whose central star has undergone a further ejection of highly processed material. It consists of a large, faint, spherical shell, in which several bright knots are embedded. The knots were first noted by Jacoby (1979), and analysis of their abundances by Hazard et al (1980) and Jacoby & Ford (1983) showed that they are extremely hydrogen-deficient.