3-D Photoionization Structure and Distances of Planetary Nebulae I.   NGC6369
  We present the results of mapping the planetary nebula NGC6369 using multiple long slit spectra taken with the CTIO 1.5m telescope. We create two dimensional emission line images from our spectra, and use these to derive fluxes for 17 lines, the Halpha/Hbeta extinction map, the [SII] line ratio density map, and the [NII] temperature map of the nebula. We use our photoionization code constrained by these data to determine the distance, the ionizing star characteristics, and show that a clumpy hour-glass shape is the most likely three-dimensional structure for NGC6369. Note that our knowledge of the nebular structure eliminates all uncertainties associated with classical distance determinations, and our method can be applied to any spatially resolved emission line nebula. We use the central star, nebular emission line, and optical+IR luminosities to show that NGC6369 is matter bound, as about 70% of the Lyman continuum flux escapes. Using evolutionary tracks from Bloecker(1995) we derive a central star mass of about 0.65 Msolar. 
Hektor Monteiro, Hugo E. Schwarz, Ruth Gruenwald, Steve Heathcote