Aligning Lens Flare To Target

In order to align the streak of the lens flare to a target, first create 2 nulls (LightTarget, LightSource)

Light Factory Location =
lSource = thisComp.layer("LightSource").transform.position;
lTarget = thisComp.layer("LightTarget").transform.position;
Anchor = transform.anchorPoint;
lSource-lTarget+Anchor

Light Factory's layer position =
thisComp.layer("LightTarget").transform.position

Make sure the solid layer that the lens flare is applied to is large enough for the comp.