Spectrophotometric observations of a peculiar nitrogen-rich planetary nebula NGC 2440

By using the Boller and Chivens spectrograph with a moderate dispersion (59 å mm^-1) in the red spectral region, we obtained 65 spectra covering the whole surface of the planetary nebula NGC 2440. Intensities of Hα, N II] λλ 6548–6584 and S II] λλ 6717–6731 lines are derived using the IDS system available at the ESO in La Silva (Chile). The nebula is known to be a nitrogen-rich nebula (Peimbert 1978) surrounded by secondary structures (Minkowski 1964). The unusual high value of the N II]/Hα in the central core (~ 30) is certainly due to the nitrogen overabundance occurring in that part of the nebula. Its variations from scale ionization structure (Capriotti, Cromwell and Williams 1971). The observations show clearly an outward increase of both NII]/Hα andI(6717)/I(6713) ratios.