I haven't looked into the relationship with the firmament, but I do know that Red Shift is nonsense.  It was debunked by a top scientist who was then blackballed in the scientific community.

It's catching on more and more now.  Just do a Google search on "red shift debunked".  There are various alternative theories about what it means, but no certainty, and it's pretty clearly understood that red shift does not prove anything about an "expanding universe".

Never heard of a bogus red shift but I'll check it out.

This section was also interesting:

Another simple explanation for redshift is the idea that nothing in in the universe can travel forever without any affect. Dr. Glenn Borchardt, known as “Mr. Infinity” and a scientist who argues against the theory of the big bang, states in his numerous books that nothing, including light can travel through space with no effect.

According to Borchardt, space is not empty and as light travels through space, it encounters resistance and therefor, by the time it gets to any observer, there will be a change – and in this case, it is frequency. This means that no matter where you are in Borchardt’s infinite universe, everyone everywhere will see redshift.

Notice the bolded.  Recall that they got rid of ether because the Michelson-Morley experiment would otherwise have proved that the earth is stationary.  This was nonsense, because "waves" cannot travel through empty space, as they required a medium.  But they got rid of it anyway.  This Dr. Borchardt seems to revive the notion that "space is not empty," i.e. that there's a medium through which the light travels.

You'll see that there's an incestuous interplay among the atheistic science agenda.

Of course, to answer your original question, if light passes through the firmament, it too would encounter "resistance".

The Doppler effect is very noticeable on sound waves. Actually you can sense it just by standing near a road where cars pass by relatively fast.

However, for observing the Doppler effect on electromagnetic waves, the relative velocity at which the emitter of the waves has to be moving with respect to the observer has to be very high, comparable with the speed of light.

I don't buy that this crazy massive objects like stars, quasars, etc. are moving at such high velocities with respect to the Earth.

Right.  I saw a presentation at one time by another scientist who demonstrated the reason for Arp's conclusion, where various observations contradicted red shift completely.  I can't recall the details now, but it was pretty compelling, and they interviewed other scientists who agreed that these observations debunked redshift as being due to Doppler effect.  No one said that Doppler effect doesn't exist, just that red shift that we see it not caused by it.

Also, regardless of the Doppler Effect, in postulating the red shift there is the assumption that there is the same abundance of chemical compounds in far away stars than in nearer stars. This might not be the case.

EDIT: This is a similar fallacious assumption than the one they use to justify old earth and radiocarbon dating: that there has always been the same abundance of radiocarbon in the atmosphere. I think that in Christian apologetics they call it "uniformity principle" or something like that.

EDIT2: Also, how do we KNOW what is the chemical composition of a star if we've never sampled one? Lol

All valid points.  They "KNOW" because they "want" to "KNOW".  Science has been in the service of the atheistic agenda since the mid-1800s (and admittedly so by some of the early rationalists).  They make things up that they feel would support their agenda and then present them as proven / established / incontrovertible fact.  Then they stack other stuff on top of these "facts" ... in a veritable house of cards structure.

That's why even Kaku admitted that we have the greatest mismatch between theory and observation in the history of science.  One bogus "fact" and assumption at the bottom gets magnified as you go up the stack layers.