I can tell you from experience mate, that there is no such thing as overkill when it comes to the stability of a pier. Even if you have solid steel, all you have to do is give it a bit of length, add some weight on top of it, and it vibrates and shakes like nothing else. You will really notice it at higher magnifications through your telescope. If you can find bigger and heavier metal, GO FOR IT! Even better, fill it with sand or cement when you're done.
FYI, I started with a telescopic 80mm gal pipe inside a 100mm gal pipe, with 10mm thick steel plates top and bottom. Shook like the Swiss family Robinson's treehouse in a hurricane.
Next, I tried bracing it with 45mm x 45mm x 5mm steel angel welded and bolted at 45 degrees. A bit better.
Finally, I put a cubic metre of concrete under the ground, then built a 300mm x 300mm square reinforced concrete pylon, up 2 metres through the Observatory floor. It doesn't budge a micron!
I also just built a pier for Ron (Tailwag) from steel I beam. It's on this forum too mate under DIY.
Hope this helps.
Baz.
