Abstract
Photoelectric spectrophotometry of emission lines in the 3400-7400A range is presented for thirty-three planetary nebulae, covering a galactocentric radial range of about 10 kpc. These observations are analyzed to obtain information about individual objects and our galaxy. The logarithmic abundances by number of a typical planetary nebula of the solar neighborhood are H = 12.00, He = 11.04, C = 9.5, N = 8.33, 0 = 8.87 and Ne= 8.28. The He/H, 0/H and Ne/H abundance ratios are very similar to those of the Orion Nebula while the C/H and N/H abundance ratios are larger by factors of nine and four, respectively. The abundance gradients evaluated at the solar vicinity are d log (He/H) /dR = -0.02 kpc-1, d log (O/H)/dR= -0.06 kpc-1 and d log(N/H)/dR= -0.18 kpc-1. A relative helium to heavy element enrichment, AY/AZ, of 2.4 is obtained. By comparing the electron density derived from forbidden lines to that derived from the total observed flux at H an average filling factor of 0.05 is found for the optically thin planetary nebulae in our sample.
