SIMBAD references

Images of NGC 6302 were taken with filters centred in most of the main optical emission lines. Extinction and electron density in the eastern lobe of the nebula are smaller. It is also hotter and more highly excited. These asymmetries may be due to an internal geometrical alignment of the disk surrounding the central star. Shock excited regions delineate the walls of the bipolar cavity. For a distance of 2 kpc, the ionized mass is around 0.12M_☉. Helium abundance is at least 0.22, significantly larger than estimates based on spectroscopic observations at only one position. The calculated ionic concentrations of O⁰, O⁺, O⁺² and N⁺ agree with previous determinations, whereas S⁺ and S⁺² were found to be twice as abundant. The determination of total abundances for these elements was hampered by lack of information on the more highly ionized species of oxygen.