Couple of things:
At "local distances" the redshift z (the offset of observed absorbtion or emission lines) approximates distance (light travel time) as an "equal" proportion of the age of the Universe: As an example, IC1101 (z~.07) is 13.7(billion years age of universe) times .07 (z) equals .931 (billion years light travel time). However, that Galaxy is about a Billion light years away right now- it has receded another 65 million light years during that time: 931mly x z(.07) -so its co-moving (current) distance is ~.997 Billion ly. (NED) disclaimer: these numbers are from memory - you get the gist.
The value of z does not increase linearly with distance: z increases logarithmically as distance increases linearly: Example: a z of 1 indicates an observed doubling of an emitted wavelength( a halving of its frequency) and as such, a recession velocity V well below the speed of light, I believe the formula is V=1/(z+1)^2 (Please feel free to check me). At z=1, the observed distance (light travel time) is about .6 the age of the universe, at z=3 it is about .9 the age of the universe, at z=7 it's about .97....
There are some current issues as to the value of the Hubble constant, and there are in fact major differences based on cosmology (flat, curved, open, hyperbolic) that affect such distance estimates materially.
Remember also that the observed recession velocity reflects the sum of the Hubble flow(not nailed down to one provably correct value yet- may not be possible) plus the source's local radial velocity( to be cosidered (near) zero for only the very largest Masscons (mass concentrations- i.e. Brightest Cluster Central elliptical Galaxies as markers of massive Galaxy clusters and super-clusters' gravicenters- love that word!).
In a nutshell, the accepted light travel time is probably nearly correct, given the above fudge factors. Use that to determine (estimate!) the co-moving distance: NED lays out the basic relationships for any Galaxy you may search on that database, fairly well.
A final point: SDSS and other surveys have collected millions of spectra of galaxies- most within the local Universe - not even close to how many remain only photometrically observed and catalogued -even among targets identifiable in amateur images. It's... humbling... and... sorry about the word salad.
Edited by quazy4quasars, 17 July 2019 - 04:10 PM.