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Old 19-11-2018, 11:03 AM
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ChrisM
Sandy Ridge Observatory

ChrisM is offline
 
Join Date: Mar 2008
Location: Gippsland, VIC
Posts: 730
Jason,
The time to cool will depend on the a few factors including total mass, surface area and difference in temperature between the pier and ambient. Whilst a larger diameter pier will provide a more stable pier (up to a point), unnecessary wall thickness won't make any noticeable difference to stability yet will take longer to cool down. Having said that, it will also take longer to heat up. If your pier will be out in the open where there is a breeze, this may not be an issue.

My pier (275 dia x 6 mm WT) sits on the top floor of a two-story observatory and heats up quite a bit during the day, so after the sun goes off the building I open the dome and entry door to allow a few hours of cooling, which is mainly for the chunky mirror, but also the obs in general.

Ultimately, use what pipe you have, or can get easily, then rigidly fix it via a solid base plate to the concrete foundation such that any movement comes from the pipe itself and not from the base plate or fixing. If the pipe is a bit slender, then add some gussets.

Cheers, Chris
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