  The SDSS-III Apache Point Observatory Galactic Evolution Experiment (APOGEE)
is a three year survey that is collecting 100,000 high-resolution spectra in
the near-IR across multiple Galactic populations. To derive stellar parameters
and chemical compositions from this massive data set, the APOGEE Stellar
Parameters and Chemical Abundances Pipeline (ASPCAP) has been developed. Here,
we describe empirical calibrations of stellar parameters presented in the first
SDSS-III APOGEE data release (DR10). These calibrations were enabled by
observations of 559 stars in 20 globular and open clusters. The cluster
observations were supplemented by observations of stars in NASA's Kepler field
that have well determined surface gravities from asteroseismic analysis. We
discuss the accuracy and precision of the derived stellar parameters,
considering especially effective temperature, surface gravity, and metallicity;
we also briefly discuss the derived results for the abundances of the
alpha-elements, carbon, and nitrogen. Overall, we find that ASPCAP achieves
reasonably accurate results for temperature and metallicity, but suffers from
systematic errors in surface gravity. We derive calibration relations that
bring the raw ASPCAP results into better agreement with independently
determined stellar parameters. The internal scatter of ASPCAP parameters within
clusters suggests that, metallicities are measured with a precision better than
0.1 dex, effective temperatures better than 150 K, and surface gravities better
than 0.2 dex. The understanding provided by the clusters and Kepler giants on
the current accuracy and precision will be invaluable for future improvements
of the pipeline.
