[Jeffkop (Jeff)]

Originally Posted by koputai

With no calculations involved, a pier of 197mm diameter and 1800mm high sounds a bit too thin for the height.

Originally Posted by ChrisM

Jeff, I made my concrete pier 450 mm dia and it's 2.2 m high. I've never detected any low-frequency vibration after the pier is struck, so I reckon that it's about the right dia/height. I agree that a 200 mm pier 1800 mm high made from concrete would seem too thin.

To avoid the potential for the pier interfering with equipment on top, and to provide a means of changing the equipment height at some time in the future, I opted for a steel pier on top of the concrete pier.

See http://www.iceinspace.com.au/forum/s...ad.php?t=36222 for a pier pic (I think at around post #7).

Chris

Thanks for these replies ... Confusion here ... but perhaps I still have a direction to head ... In my reply to Al I suggested that I was thinking of a 250mm size with a reduction down to 180mm over the top 30mm or so. It looks as though the 250mm is still too conservative however.

My suggested 1800mm high is probably a little over estimated too. Its based on this:

If the wall height of the observatory is 1500mm I would imagine I would have to have the scope sitting to at least 500mm of that.

So that equates to 1000mm in the observatory and I reckon it will be 400-500mm to the ground ... so the overall length of the pier somewhere around 1400-1500mm

Thanks again for your inputs

Jeff