  Recently collected SNIa data have been used to address the problem of
measuring the cosmological parameters of the universe. Analysed in the
framework of homogeneous models, they have yielded, as a primary result, a
strictly positive cosmological constant. However, a straight reading of the
published measurements, conducted with no a priori idea of which model would
best describe our universe, at least up to redshifts z=1, does not exclude the
possibility of ruling out the Cosmological Principle - and cosmological
constant - hypotheses. It is here shown how the large scale (in)homogeneity of
this part of the universe can be tested on our past light cone, using the
magnitude-redshift relation, provided sufficiently accurate data from sources
at redshifts approaching z=1 would be available.
