This is kind of misleading, interstellar could suggest looking across space which we already do. Let me explain: Every year astronomers look at the sky when the earth is on opposite sides of the orbit around the sun and use parallax. However, New Horizons is a lot farther away. I remember from my middle school science class (it was a really good one, what was that guy's name), that they used the tiny differences to find the distance to some nearby systems, if I recall correctly. The distances were so huge, the change in angle across the solar system so small, it was an amazing idea at that age.