The redshift distance modulus modz , in mag, is derived from the Virgo infall vvir , it can be used to determine the absolute magnitude knowing the apparent one. It is defined as modz = 5 log(D L ) + 25 where D L is the luminosity-distance in Mpc, defined by the law of dimming of the observed flux: F L / D L 2 . ... D L is derived from the cosmological redshift, assuming the following values for the Hubble constant and other cosmological parameters: H 0 = 70 km/s/Mpc . ...