Comoving transformation

[Edgard Neuman]

Hi,

My question is the following :

Consider two observers, in the univers, who have no speed in their comoving reference frame.

They see their univers having the same age, but they are very far from each other, a distance almost as big as their visible univers.

Other objects they see (stars) are at various distances.

What is the form of the transformation that apply to coordinates of other objects they both see, (including the effect of the expansion) ?

And can it be compared to transformation of speed in special relativity

[

something like v' = v+w / (1+(w*v))

where speed are expressed in fractions of c

]

To simplify the problem, we can considere only one spatial dimension.