  With the Delta a photometric system, it is possible to study very distant
galactic and even extragalactic clusters with a high level of accuracy. This
can be done with a classical color-magnitude diagram and appropriate
isochrones. The new calibration presented in this paper is a powerful
extension. For open clusters, the reddening is straightforward for an
estimation via Isochrone fitting and is needed in order to calculate the
reddening-free, temperature sensitive, index (g1-y)0. As a last step, the
calibration can be applied to individual stars. Because no a-priori
reddening-free photometric parameters are available for the investigated
spectral range, we have applied the dereddening calibrations of the Stromgren
uvbybeta system and compared them with extinction models for the Milky Way. As
expected from the sample of bright stars, the extinction is negligible for
almost all objects. As a next step, already established calibrations within the
Stromgren uvbybeta, Geneva 7-color, and Johnson UBV systems were applied to a
sample of 282 normal stars to derive a polynomial fit of the third degree for
the averaged effective temperatures to the individual (g1-y)0 values with a
mean of the error for the whole sample of Delta T(eff) is 134K, which is lower
than the value in Paper I for hotter stars. No statistically significant effect
of the rotational velocity on the precision of the calibration was found.
