As several aspect of my original project many changed are made.
That's the case for the pier.

I made two modifications: I reduced the lentgh of the tube from 39" to 31"(100cm to 80cm)
By the way I modified the base of the pier to improve the Polar longitude alignment.

To do that I made three metal plates. One to support the pier by the concret, a second one to ajust the horizontal situation of the pier and the last one is to rotate the pier on its latitude..