SNIa data to probe the Cosmological Principle

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.