The circle was cut with a router before the split was cut out, and then it was smoothed by rotating it against a belt sander.
Angle irons help reinforce the thinest section of the ring.
The stepper motor for the declination tangent arm is also visible in this photo. The wires for the dec drive, dec encoder, cooling fan, and focuser run inside the yoke and ring. The wires were layed into routed grooves before the two plywood layers were glued together. The cradle holds the ring assembly and provides the R.A. bearing. The drive assembly and R.A. stepper motor are located between the plates.