Quote:
Originally Posted by plasmodium
Decisions decisions now - thanks for all the excellent advice guys.... I'm starting to lean more towards the concrete pier (prob 250mm) for a couple of reasons:
1. seems to be better in terms of vibrations etc than similar steel.
2. cheaper - I'm going to need a big plug of concrete regardless - adding the pier whilst pouring won't be too onerous
Obviously my first point of portability comes up - but to move a steel pier I'd still need to pour another big monolith! - my initial 5mm thick pier I calculated would weigh 52kg or so, so with 10-12mm steel and more ribs etc it would likely hit 80kg plus.....
Will keep brainstorming......
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There's a lot of merit in using the concrete filled pipe, Lee.
Though I don't have a pier/observatory I have been thinking about it for a while, with the intention that when I move to a site with less light pollution I'll build one. For what it's worth, my preferred solution for a pier at this stage is an 8 to 10" concrete pipe set vertically into a concrete footing at least 600x600x600. The pipe would be cut off at the required height and filled with concrete. Chemsets and grout under the adapter plate for the mount on top.
Should be rock solid...
The concrete filled plastic pipe should nearly as good (I wonder if you could tell the difference in performance?
).
Just food for thought...
Al.