We know of an ancient radiation
That haunts dismembered constellations
A faintly glimmering radio station
— Cake, Frank Sinatra
This page has a calculator useful for answering those questions that come up when you're in talks or writing telescope proposals, like How many kpc correspond to 1 arcminute at redshift 3?, How bright is an L* galaxy at redshift 1.5? or What is the lookback time to redshift 2?.
|Distance (Mpc) per arcmin||Hubble parameter (km/s/Mpc)|
| Elapsed time since the emission of a
photon with redshift z (Gyr)
| Rest-frame apparent b magnitude
of a Mb = -21 galaxy
Take a look at some other popular cosmology calculators.