Combined kinematic and cosmological redshift
= Combined kinematic and cosmological redshift
{title2=$1+z_{\rm tot}=(1+z_{\rm cosm})(1+z_{\rm kin})$}
Frequency ratios multiply when a photon is transformed first between a source and its local comoving frame, then propagated through an expanding universe. Thus the <kinematic redshift> and <cosmological redshift> factors multiply. Their redshifts themselves add only to first order when both are small.