or are determined using *g*- and *r*-band photometry available from the Sloan Digital Sky Survey [SDSS; @york00]. The SDSS values are then used to estimate the $B-V$ color following @jester05: $$B-V = \frac{(g-r)+0.22}{1.02}.$$ The available $M_B$, $M_{[4.5]}$, and $B-V$ colors and references for this sample are listed in Table \[tbl1\]. Note that the main source of uncertainty in these magnitudes lies in the distance determinations. Eight of the objects in our sample have distance errors of approximately $10\%$. Furthermore, 20 of the 44 objects in our sample do not have uncertainties associated with their distance determinations. For these objects we used an uncertainty of $10\%$, which may be an underestimate for some of them. The distance uncertainties tend to dominate over the photometric uncertainties.

NEBULAR ABUNDANCE ANALYSIS {#sec:data}
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Emission Line Measurements {#sec:iraf}
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Emission line strengths were measured using standard methods available within IRAF[^4]. In particular, the SPLOT routine was used to analyze the extracted one-dimensional spectra and to fit Gaussian profiles to emission lines to determine their integrated fluxes. Special attention was paid to the Balmer lines, which are sometimes located in troughs of significant underlying stellar absorption. The H$\alpha$ emission lines typically had equivalent widths of $\sim$ 