  We demonstrate how the metallicities of young super star clusters can be
measured using novel spectroscopic techniques in the J-band. The near-infrared
flux of super star clusters older than ~6 Myr is dominated by tens to hundreds
of red supergiant stars. Our technique is designed to harness the integrated
light of that population and produces accurate metallicities for new
observations in galaxies above (M83) and below (NGC 6946) solar metallicity. In
M83 we find [Z]= +0.28 +/- 0.14 dex using a moderate resolution (R~3500) J-band
spectrum and in NGC 6496 we report [Z]= -0.32 +/- 0.20 dex from a low
resolution spectrum of R~1800. Recently commissioned low resolution multiplexed
spectrographs on the VLT (KMOS) and Keck (MOSFIRE) will allow accurate
measurements of super star cluster metallicities across the disks of
star-forming galaxies up to distances of 70 Mpc with single night observation
campaigns using the method presented in this letter.
