  We have re-observed $\rm\sim$40 low-inclination, star-forming galaxies from
the MaNGA survey ($\upsigma\sim65$~\kms) at $\sim$6.5 times higher spectral
resolution ($\upsigma\sim10$~\kms) using the HexPak integral field unit on the
WIYN 3.5m telescope. The aim of these observations is to calibrate MaNGA's
instrumental resolution and to characterize turbulence in the warm interstellar
medium and ionized galactic outflows. Here we report the results for the
H$\rm\upalpha$ region observations as they pertain to the calibration of
MaNGA's spectral resolution. Remarkably, we find that the previously-reported
MaNGA line-spread-function (LSF) Gaussian width is systematically
underestimated by only 1\%. The LSF increase modestly reduces the
characteristic dispersion of HII regions-dominated spectra sampled at 1-2 kpc
spatial scales from 23 to 20 km s$^{-1}$ in our sample, or a 25\% decrease in
the random-motion kinetic energy. This commensurately lowers the dispersion
zeropoint in the relation between line-width and star-formation rate
surface-density in galaxies sampled on the same spatial scale. This modest
zero-point shift does not appear to alter the power-law slope in the relation
between line-width and star-formation rate surface-density. We also show that
adopting a scheme whereby corrected line-widths are computed as the square root
of the median of the difference in the squared measured line width and the
squared LSF Gaussian avoids biases and allows for lower SNR data to be used
reliably.
