I believe that we are all arguing at cross purposes here. Dehammer has a point when the firts observer measures light speed and the speed of the second obserrver relative to the inertial reference frame of the first observer. He will then see that the second observer catches up partially with the light moving away from the second observer; i.e. the light moves away at the speed c-v where v is the speed of the second observer. If this were not so there would not have been a Doppler shift for light; however, the second observer will still observe the light moving away from him as moving with a speed c relative to his own reference frame. In special relativity it is of utmost importance to carefully specify the reference frame relative to which an observation is being made. It is for this reason why two observers moving relative to each other can differ on whether two events are simultaneous. If it is simultaeous in one reference frame it is not so in the other.
