Peter,
Another idea is to incorporate a stubby (ie. not full height) concrete pier with the pier foundation, which typically would also be concrete. Then, a steel pier can be attached to the top of the concrete pier to attain whatever height is needed. Future equipment changes can be accommodated by replacing the relatively cheap steel pier with a shorter or longer one.
I used this concept for my two-storey observatory - refer to some basic details and pictures here:
http://www.iceinspace.com.au/forum/s...t=36222&page=2
I bought a length of Formtube from the supplier in West Heidelberg, Melbourne, and would be surprised if there wasn't an equivalent in your part of the country.
Chris