Photoionization modeling of the Galactic planetary nebulae Abell 39 and
  NGC 7027
  We estimate distances to the spherical planetary nebula Abell 39 and the
bipolar planetary nebula NGC 7027 by interpolating from a wide grid of
photoionization models using the 3-D code, MOCASSIN. We find preliminary
distances of 1.5 kpc and 0.9 kpc respectively, with uncertainties of about 30%.
