Hi Greg,
your scope is not that heavy (around 1.5kg plus eyepiece and prisma) - depends basically on the quality of the geared head and the ballhead if it's possible to mount it on the Astrotrac.
You could screw a dovetail clamp (like this one e.g.:
http://www.teleskop-express.de/shop/...her-Level.html onto the ballhead and mount the scope on a suitable dovetail plate (
http://www.teleskop-express.de/shop/...le---21cm.html) which makes it easy to balance the scope when You're switching eyepieces or decide to use a prism.
We used a Astrotrac mount during our holidays for imaging with a Canon EOS 450D + Battery Grip + 300mm/f4 lens and 1.4x converter (3.5kg +) on a Manfrotto ballhead without any problems at all.
Cheers,
Steffen