Sometimes two planets are close to being in aspect to each other, but they're too far away to be within a reasonable orb. Ordinarily, these planets would not be considered in aspect to one another. However, if a third planet forms an aspect to both of them, that third planet can act as a bridge or "middle-man" that joins the other two planets. This is called "Collection of Light."
This actually happened at the New Moon in Leo in July 2006. As the Sun moved up to conjunct Saturn, it too created a collection of light that bridged the gap between Chiron and Neptune.