Distance modulus: mod0

When measurements are available in the distance catalogue, mod0 is computed as the weighted average of those measurements.

Another parameter, modz (redshift distance modulus), estimates the luminosity-distance using the redshift. mod0 is essentially available for the closest galaxies for which the peculiar motions of the galaxy would make modz ineffective, while this latter, available for a wide redshift range, complement it when the recession velocity if greater than a few 1000 km/s. The two parameters, mod0 and modz are combined together to provide an homogeneous distance estimate over the whole redshit range: modbest.