I built up additional rebar, and a pair of 1 inch electrical conduits up into a 12 inch diameter 48 inch tail concrete tube form. I poured in 3 bags of concrete and made sure the tube was level and the rebar and conduit was well centered. When pouring the concrete I use a stick to tamp down the concrete to be sure there were no air pockets around the rebar.
Saturday night when Polaris was visible I used a small telescope with a cross air eye piece to align with Polaris on my Discmount DM-4. I put a 8 foot long straight stick on the saddle of the mount and made sure it was aligned across the center of the concrete tube. I made a north and south alignment mark.
Here is a view of my top plate. I used 4 24 inch sections of 5/8 inch threaded rod to support the top plate. The bottom 3 inches of rod was bent over 90 degrees to keep them from turning. I bought a 12 x 12 inch 1/4 steel plate and used my grinder to cut it into a hexagon shape.
I finished the pour of concrete on Sunday. I filled the remaining portion of the tube and set in the top plate with the all thread rod. I verified the bolts and alignment marks matched and the top plate was level. The nuts can be moved up or down as needed after the concrete cures for 7 days for final leveling if required.
I used a pair of 2.75 pound weights as spacers on the top of the pier plate. I bolted the plates to the 1/4 steel plate and put in an azimuth alignment bolt for the Atlas. The Atlas head set on the center of the top plate and be bolted down using a short bolt with hand knob that was included with the Atlas pier mount extension.
Jeff