I struggled at first because I couldn't actually get to the edge of the map to see the silver ball (or the correct blimp for that matter as I assumed it was the massive one). The screen just wouldn't scroll to the edges of the map for some reason.

Anyway I have managed to get around this and thought I would share the info in case anyone else is having similar problems. The fix is easily done by changing the resolution from 1440x990 to 1024x768 (in my case anyway). You can then move around the entire map (and swap back to a higher res once your at the edge.)

Dunno why but I'm assuming it's a problem with widescreen resolutions.

(running steam version with RoS mod).