While a ship is at warp, one can normally observe the image of the stars being distorted due to the speed of the ship. You can imply if you see the stars "approach" the ship, that they then pass it, and can be seen on the back of the ship "moving away". But in Star Trek: First Contact, when the Phoenix makes its first warp "jump" you can clearly see the stars pass it, even though the ship never leaves the solar system. Why is this?