Magnetascopic interference is a type of interference caused by some protostars, which impaired the function of most starship sensors. The directional array of a Galaxy-class starship was capable of cutting through the interference, but it had a very narrow scan field.
While undercover within the Maquis in 2370, Ro Laren took advantage of magnetascopic interference in the Topin system to steal medical supplies from the USS Enterprise-D. (TNG: "Preemptive Strike")