Why cloak fails

"There are alot of chronitons coming out of the anomaly," explained Lieutenant Tyvya then. "After a time, they cumulate on shields and hulls, in effect 'powdering the invisible man' and thus making any cloaked ship detectable. Adjust your tactical sensors to chroniton emissions and when you spot a mass of it moving in a predetermined cohesive pattern without dissipating, then you got a target. An unshielded target I might add."