trying to get the following effect (example with spheres). I want to clone an object multiple times around a centralised pivot point.

I used 'duplicate with transform' to get the desired effect, but it only works once.
'duplicate' gives the option for multiple objects, but it dumps them all on top of each other, instead of spreading them around the circle.
i'm guessing i might have to add a translation factor as well as rotation? but trying to work out the distances is a bit trial and error. Is there an accurate way of doing this?
thanks guys

Adam.