When exploring the map activate all three bluescreen computers.

1: In the room with Double Tap and the Mac 10.
2: In the room with the portrait of Cave Johnson.
3: in the room with the Half-Life Entropy Zero 2 reference. (The room that the cargo elevator brings you too)

After activating all the computers activate the ending elevator, enter the ventilation shaft, and interact with the extended relaxation observatory computer.