  As the second step in our investigation of the mass-to-light ratio of spiral
disks, we present the results of a spectroscopic survey of planetary nebulae
(PNe) in five nearby, low-inclination galaxies: IC 342, M74 (NGC 628), M83 (NGC
5236), M94 (NGC 4736), and M101 (NGC 5457). Using 50 setups of the WIYN/Hydra
and Blanco/Hydra spectrographs, and 25 observations with the Hobby-Eberly
Telescope's Medium Resolution Spectrograph, we determine the radial velocities
of 99, 102, 162, 127, and 48 PNe, respectively, to a precision better than 15
km/s. Although the main purpose of this data set is to facilitate dynamical
mass measurements throughout the inner and outer disks of large spiral
galaxies, our spectroscopy has other uses as well. Here, we co-add these
spectra to show that to first order, the [O III] and Balmer line ratios of
planetary nebulae vary little over the top ~1.5 mag of the planetary nebula
luminosity function. The only obvious spectral change occurs with [N II], which
increases in strength as one proceeds down the luminosity function. We also
show that typical [O III]-bright planetaries have E(B-V) ~ 0.2 of circumstellar
extinction, and that this value is virtually independent of [O III] luminosity.
We discuss the implications this has for understanding the population of PN
progenitors.
