Observing

When you are observing a creature, you can directly perceive the creature with a precise sense. Generally, this occurs when a creature is visible, when the situation makes it impossible for the creature use Stealth to hide, or when you have succeeded at a Perception check to search for the creature using a precise sense such as blindsight. You must be observing a creature to use a ranged effect that targets a specific creature without requiring an attack roll to hit (such as magic missile). You can also make normal attacks, including ones using ranged abilities, against creatures that you are observing. Again, it is subject to area effects that affect its location.

A creature currently being observed can’t attempt a Stealth check without first breaking that observation. To break observation, the creature must either mask itself from your precise senses (with darkness, fog, invisibility, or the like, but not with effects such as displacement that still leave a clear visual indicator of its location), move somewhere it can’t be observed (a place with cover, for example), or use Bluff to create a distraction to momentarily break your observation of it.