So I understand that special relativity is all about the frame of reference and there is a lot to do with time dilation and how space-time is warped at velocities near $c$. So my question is what about an observer on Earth, watching two ships accelerate, in opposite directions, away from the observer at say 1g. As they pass a velocity between the observer on Earth and a ship of .51 , cant the observer on earth measure both of them going at .51c? At which point, with respect to the observer, they are moving away from each other at 1.02c? Now special relativity says the two ships would be moving away from each other at $(v+u)/[1+(vu/c^2)]$, but how does that relate to the stationary observer?
Thanks for your help on this a co-worker and I were unable to find another reference.