Direct imagery and long-slit , spatially resolved echellograms of the high excitation planetary nebula NGC 1501 allowed us to study in detail the expansion velocity field , the physical conditions ( electron temperature , electron density , ionization ) and the spatial distribution of the nebular gas .

An electron temperature of 11500 K and a turbulence of 18 km s ^ { -1 } are derived by comparing the H \alpha and [ OIII ] emission line profiles , but large , small scale fluctuations of both these quantities are present in the ionized gas .

The radial density distribution shows external peaks up to 1400 cm ^ { -3 } ; they have steep outwards profiles and extended inwards tails probably originated by Rayleigh-Taylor instability and winds interaction .

The complexity of the expanding motions indicates that the main part of NGC 1501 is a thin ellipsoid of moderate ellipticity , but the presence of a pair of large lobes along both the major and the intermediate axes and of a multitude of smaller bumps spread on the whole nebular surface , makes the general 3-D structure of NGC 1501 like a boiling , tetra-lobed shell .

This peculiar morphology can be qualitatively explained in terms of interaction of the slow nebular material with the intense and fast wind from the WC4/OVI central star .