Z redshift

Astronomers calculate red or blue shift values by the following formula:

( f_emitted - f_observer ) / f_observer

Where f_emitted is the frequency of the emitted radiation

f_observer is the frequency of unshifted radiation seen by the observer

The following table gives the approximate equivalence between Z and the age after the Big Bang. The figures were obtained using Ned Wright's Cosmology Calculator using the values Ho = 71, OmegaM = 0.270, Omegavac = 0.730 assuming a flat universe.