make sure that you deploy the artillery, hit either F8 or the button on the console with the gard commands and stuff
  - units must be visible to bombard, even if only momentarily like when ties circle around
 -check out 
www.jediknight.net) (
http://www.jediknight.net) there are artillery strategies there including the better one from your truely using ties, form a skirmish line in front of artiller with AT's of varyine type and have an AA near your arty to defend from air attack
 -deploy the guns and you'll see reb flare type shots being fired, the circle is the blast radius for damage.
 - put turrets and 1 or 2 artiller at your bas and it will be a real stronghold inpenitrable to your enemies. 
 - i did the whole sarpin levels without artiller before i figured out how to use them, i would have suffered alot less causualties if i used them well, i figured out how to used them on yavin. 
 StS_Maryjane 
 try this out it works 
 ------------------
 StS_MAryjane, 
 You are only half as smart as you think I am