"qedude" wrote in message
...
I'm hoping someone can help me with a problem I am having. I have a
telescope
mounted on a 54 inch tall, 3/16 inch wall, 8x8 square aluminum tube with
1.25
inch plates welded to the top and bottom and bolted to 2/3 of a yard of
concrete. The problem is I am getting a little too much movement out of
the
tube and I need to increase the stiffness of the tube

Why not get rid of the aluminum tube and get a piece of cardboard sonotube
and fill it with concrete, maybe put a couple of lengths or rebar in it for
good measure. (Obligatory Metalworking Content!!)

John