OM count rates of different spectral types in different passbands
were simulated with OSIM.
The OM count rates are converted into OM magnitudes applying an
zero point correction of 18.5 mag.
The expected standard magnitudes of the various spectral types
are taken from Zombeck.

The pre-launch colour transformation coefficients
and the associated errors are calculated using the methode described
by Harris et al. (PASP 1981, **93** 507).
Harris' recommendation is followed and the colour transformation
is defined as quadratic function of the colour terms.
The equations are solved by a multilinear regression.

Michael Smith 2011-09-20