I started with an old department store refractor tripod. Sat in front of it on my roll-around shop stool and tried to picture using it with a lawn chair. That won't work, have to re-position to rotate.
Next thought was mount the tripod and the chair on some sort of lazy susan so it could rotate. Cumbersome, not steady, legs to too short to reach off the platform to rotate. EPIPHANY! The old office chair in the shop office.
1" square aluminum tubing cut and bolted to the arms of the chairs, 4" above the armrests. Four 15" pieces were cut for the articulated arms. Two pieces of tubing 5" long were used to bolt to the top arm to mount the top mount plate. A piece of T6 aluminum, 5" x 22" was cut for the top plate.
After all the cutting, deburing, drilling and the solid mount pieces were added it hit me. The arms on the chair are not square, they are wider in the front than on the back of the chair. This will cause the arms to be wider when extended fully than when they are collapsed at any other position. Thought long and hard about how to square the mounts so they were parallel with the movement and couldn't come up with anything so decided to press. Turns out they have enough flex to work.
Another problem caused by the arms not being square is the short top tubes that hold the mount plate bind pretty badly but in use it turns out this is not a problem. Once adjusted to position in the chair they don't have to move again. Leaning back in the chair does the elevation scanning just fine. Two basic positions allow me to scan from the horizon to zenith.
The biggest problem I had on this project was working out the order of flat washers and nylon flat washers to get the arms to move smoothly, tight enough to hold the weight and not back off the bolts. I wound up double nutting the bolts even with nylon lock nuts. It takes a BUNCH of tight to keep the joints from slipping.
I mounted the tripod adapter on the plate using a cut off piece of 1/4" x 20 bolt screwed into the adapter and a knob I got at Lowe's. Took the chair out for a view during the daylight and was dissapointed to find that I could see my heartbeat in the view. I thought 4 hours of work was down the tubes because the chair or the arms were not stable enough. Grabbed the mount arms to move them out of the way and get up and noticed the binos wiggling back and forth. AHA! The plastic tripod adapter that came with the binos was gently twisting back and forth. Ran inside and got a neck pillow and wrapped the binos with them and steady view!
Here I am getting ready for second light in the binos and first light for the chair.