Ships will have stealth ratings for their hulls that passively affect their detectability.
Ships' thrusters will have stealth ratings for their real time detectability while firing.
Weapons will have stealth ratings for their real time detectability while firing in the case of beams or while their shots are traveling through space in the case of projectiles.
Sensors will not be able to detect objects occluded by other objects and will be less effective at detecting objects farther away.
Sensors will have active and passive detection modes. Sensors in active mode will be more effective but decrease their own ship's ability to evade detection.
Ratings for stealth and detection can be specific to distinct bands, such that a sensor that only detects in band X will not detect a ship only visible in band Y.