The structure of the shell of HR Del

We present IIST/WFPC2 imaging of HR Del in filters centred on the lines of Ha, [N-II] and [OIII], with corresponding WIIT/ISIS slit spectroscopy for the lines of Halpha, Hbeta, [NII] and [OIII]. The data show that the ejected shell of HR Del is bipolar in structure with an equatorial ring, and polar rings or caps. The shell is composed of many small, bright knots and diffuse material which flows radially outward from these knots. Three-dimensional models of the shell that reproduce the observed emission-line images and longslit spectra in both the [OIII] and Halpha morphologies are presented. A large, bright [OIII] knot is apparent in the imaging that we cannot associate with emission in either Halpha or [NII] or the spectroscopy. In addition there are [NII] and [OIII] knots at both higher and lower velocity than that of the main shell which are symmetrically placed to either side of the central system. We estimate an inclination of 35 +/- 3degrees, a polar expansion velocity of 560 +/- 50 km. s(-1), an axial ratio of 1.75 +/- 0.15 and a distance of 970 +/- 70 pc.