as a dome is typically a hemisphere, [this topic about building spheres][1] might be very useful for you. theres also an [automatic tool to construct spheres][2] that you could use to get an [ldraw][3]-plan.


  [1]: http://bricks.stackexchange.com/questions/549/is-there-a-technique-or-algorithm-for-building-spheres
  [2]: http://lego.bldesign.org/sphere/
  [3]: http://www.ldraw.org/