How can you map the differences between Javascript objects?

In astronomic observations, how do you deal with the time differences between multiple objects observed?

• As one planet might be 100 light years away and another 200, the position of both is never really what we see. How can you actually find out the distance between the two? The only way I can imagine is observing motion and calculating the movement. But that seems hardly possible when every planets gravity influences others for more than 100 years back. Edit: I changed the description as it wasn't as clear. I used the creation of a galaxy map as an example for why you would want to do this.

• Answer:

  I don't have any extensive knowledge in astronomy; far from it but I agree with -- that the distances are not taken into account. We cannot perceive, think, or sense events happening outside our light cone.  I don't think current day astronomers are that worried about answering questions like "what is happening in the andromeda galaxy RIGHT NOW? ". For all we know it may have annihilated itself; we will not come to know until 2 million years later. Since the speed of light is the limit of information transfer, it does not make much difference what is happening right now in a distant galaxy.  As regards the position of gallaxies, I don't think there is any reliable method that astronomers can employ to obtain the concurrent position of a galaxy or faraway object and it is not worthwhile the effort anyway.