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Published online by Cambridge University Press: 19 July 2016
Long slit low resolution (3.4 A) spectra of the planetary nebulae NGC 6543 and NGC 6826, obtained using the 2.5-m Isaac Newton Telescope (La Palma) with the Image Photon Counting System (IPCS), indicate different physical conditions in the outer halos than in the central zone, with an outward increase of electronic temperature. The estimated mass contained in these halos is considerably larger than the values of the inner nebulae.