'twas first seen in "encounter at farpoint". Saucer seperation was first seen in Farpoint, but the first time it was done for tactical reasons was against the Borg "The Best of Both Worlds, part II". All instances of saucer separation: Encounter at Farpoint, Part 1 (to save civilians from Q) The Arsenal of Freedom (to defeat the Minos weapon) The Best of Both Worlds, Part 2 (to distract the Borg) Star Trek: Generations (to evacuate the doomed Enterprise)