Wow so many good ideas ! Some responses below.
The pier is completely isolated from the observing deck. The hole goes down about 42 inches into fairly dense soil. At the 36 inch mark I hit a layer of large stones that appears to go in for a while. The shape of the footer is like a pyramid with the top chopped off. Someone asked about pouring a concrete pier. While this is a great idea for a pier it creates a problem if you ever want to move. Someone also mentioned pouring concrete into the pier - This is a real no no with aluminum. The concrete will corrode aluminum in no time.
Someone asked how am I measuring this ?
Laser pointers :-) Clamp a laser pointer or in my case last pointers to the pier and aim them at a target some distance away. This is how I can be fairly sure that the pier itself is flexing. I can't be 100 percent sure since the laser pointers don't give a really precise dot. I can also see this in the eyepiece of the scope using a high power cross hair eyepiece.
Someone asked about the pier to concrete mounting.
I imbedded 3/4 inch jbolts 18 inched into the concrete. I leveled the top of the concrete with a sheet of thick plexiglass so that it was level and smooth. The bottom of the pier is flat to a very good straight edge. I used large washers below the nuts and I tightened the nuts to 100 ft lbs.
I did an experiment last night. I took some 1.5 x 1.5 steel tubing and I roughed it up with a 40 grit sanding disk. I clamped the tubing very tightly to the pier with some homemade H clamps. This appears to have really helped perhaps enough to allow me to image. Unfortunately clouds rolled in before I could try the camera. So I am thinking of welding a rib down sides of the pier as step one. I still want to try adding the tensioning rods as well to see if that improves it more. I also started cleaning up the steel pipe last night as well as I may end up going that way.
Scott Hogsten