Okay - why it is so good - crossfire zones.
It can create a doghnut shaped fire zone about it's pylon in the X/Y plane, and to a lesser extent, the Y/Z plane :
Imagine the Foward set of decks as a sphere, and the rear, egine section of the ship as a sphere. Now have lines radiating out, from their centre, in all directions. On their own, you have a lot of lines - an ugly windmill if you like.
However, join these two spheres by a pylon (rectangle in between of rough scale), and remove lines that would indicate the ship shooting itself, and you will find that above and below the pylon, a pattern of over crossing lines. These are it's crossfire zones !
If a nebulon got between home ship and fighters, the Allinace force is screwed !
Hows THAT for a theory !
Nova Squadron, the Elite B-Wing flight group stationed aboard the Nebulon B Frigate 'Oracle', home of the tech library.
'No capitol too large, no corvette too armed. NOVA squadron, for ALL your extermination needs. Our special at the moment - SSDs (See our work with the Iron Fist !) !'
Commander Jon 'DFMD' Adamson - leader of Nova Squadron (B-Wing ID = 'The White Witch')