Oh man, I'm messed up. I wrote a reply and somehow just deleted it. Here we go again.
a1-a3, b1-b3, c1-c3...etc are points were oponents weapons will hit your ship.
a1-a3 are points that will be hit if the weapons fire comes from a direction that is between 30 degrees to the port and 30 degrees to the starboard of your ships centerline at the bow.
b1-b3 are points that will be hit if the weapons fire comes from the 60 degree arc that is between 30 degrees to starboard and 90 degrees starboard. Basically the right front of the ship.
c1-c3 will come from 90 degrees and 150.
d1-d3 will come from 150 degrees and 210. Which is basically aft.
e1-e3 will be fire that comes from 210 to 270.
f1-f3 comes from 270 to 330.
I'm having problems with my thoughts so if this isn't understandable I apologize.
So lets say when you put the a1 a2 and a3 dummy objects in the ship you envision what can be hit by a weapon that is fired from the front.
Front of saucer, bridge, front of nacelle, top of forward hull stuff like that. Only thing to keep in mind is that most of the fighting is done from the f3 view which is behind and a bit above so you'll want to choose spots that can be seen from that view.
I can try to explain better, if needed, when I get over this.