used, yielding an approximate dispersion of 1.2 Å per pixel, a full width at half maximum resolution of $\lesssim3$ Å, and a wavelength coverage of 3690–6790 Å. The sensitivity, resolution, and wavelength coverage of the MMT and Blue Channel spectrograph combination allowed for the measurement of all emission lines relevant to oxygen abundance determinations. Bias frames, flat-field lamp images, and sky flats were taken each night. The latter were primarily necessary due to significant differences between the chip illumination patterns of the sky and the MMT Top Box that houses the “BC" incandescent flat-field lamp. On average, four standard stars from @oke90 with spectral energy distributions (SEDs) peaking in the blue and containing minimal absorption were observed throughout the night using a 5$\arcsec$ slit over a range of airmasses. This allows the flux calibration to be determined as a function of airmass. The large slit width mitigates the effects of atmospheric differential refraction and allows accurate measurements of relative fluxes across a large range in wavelength. Note that since we only care about relative abundances, an absolute flux calibration is not critical.

All 44 galaxies had at least one strong H$\alpha$ brightness peak that was aligned with the $1\arcsec\times180\arcsec$ slit. 