Hi Alistairsam,
Sorry I seem to be mixing up my mount attacahments in my head. For some reason I thought you could use the equatorial mount for polar alignment and attach the astrotrac on to that but i don't think you can.
From what I can gather, the astrotrac is mountable on a standard tripod mount. To do the polar alignment, they suggest a manfrotto geared head (which is around us$200+ anyway) but I don't see why you can't do this with a simple pan and tilt or ball head. It just won't have the fine-tuning. On the astrotrac website, they sell a kit with the geared head, tripod and ball head (
http://www.astrotrac.com/Default.aspx?p=holiday-deal) but the mount is not rated for high enough load for the scope + camera + mount (around 5kg). The image that you linked it looks like the telescope is mounted directly to the astotrac which is interesting. Also, he has the wedge but that's another $300+
Unfortunately, my current tripod is only rated for 4kg (since my camera and lens is only around 0.5kg) so I'd have to get a new one anyway.