  We present results for the mass splittings of low-lying charmonium states
from a calculation with Wilson clover valence quarks with the Fermilab
interpretation on an asqtad sea. We use five lattice spacings and two values of
the light sea quark mass to extrapolate our results to the physical point.
Sources of systematic uncertainty in our calculation are discussed and we
compare our results for the 1S hyperfine splitting, the 1P-1S splitting and the
P-wave spin orbit and tensor splittings to experiment.
