  We present a fast (<< 1 s per profile) inversion code for solar Ca II lines.
The code uses an archive of spectra that are synthesized prior to the inversion
under the assumption of local thermodynamic equilibrium (LTE). We show that it
can be successfully applied to spectrograph data or more sparsely sampled
spectra from two-dimensional spectrometers. From a comparison to a non-LTE
inversion of the same set of spectra, we derive a first-order non-LTE
correction to the temperature stratifications derived in the LTE approach. The
correction factor is close to unity up to log tau ~ -3 and increases to values
of 2.5 and 4 at log tau = -6 in the quiet Sun and the umbra, respectively.
