Thanks Orac. Lots to think about there, not least the tendency of experts to over complicate!

What I said was:

"Observer 2 is travelling (in the direction from detector to emitter) at 0.8c."

I didn't say he was travelling between the two at any point. However, I take your point that I should have been more specific. I didn't say if observer 2 was travelling towards, or away from the set-up. My bad. frown

There never was nothing.