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pier mov't
My pier seems to move a bit as well Fred. My PME sits about 2m above the base of the concrete pier, which is founded in apparently massive sandstone. The lower half of the pier is about 500mm square. A steel pipe goes up the middle and carries the mount base.
I found my guiding was erratic of late (using an OAG) - after redoing some largish Tpoint models I found that alignment had shifted noticably. After realigning, guiding has improved again.The geology in my area has sandstone interbedded with shales and claystones so I guess the sandstone foundation is subject to either hydraulic effects along discontinuities in the bedrock or some reactive clays or both.
Seasonal checks on polar alignment are on the menu as a result.
guy
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