Top down, eh? I'll have to give that a try. Usually I just forfeit nebula missions since I can't seem to get room to manoeuvre. Thanks for the tip.
The game warns you if you are heading for a collision with Planets, asteroids, or radiation bursts within a nebula. If you don't see anything on your tactical screen, don't sweat it too much. It usually is only a problem if your in a Saber or other small ship with weak shields. Within the SFC configuration file, you can turn off these warnings. But you'll then have to be very wary of getting to close to planets and especially asteroids. My advise; live with it or turn down your voice volume setting.
At the top of the configuration settings file, look for this:
[Game]
DeathCam=1
BorderAlert=1
CollisionAlert=1
DifficultyLevel=0
AutoFilm=1
TargetDirection=1
RaceShieldFX=1
Change the CollsionAlert value to zero.
BTW, if your RaceSheildFX is set at zero, changing it to 1 will give each race its own color
when struck by weapons fire.