24" chimney pier for the 18"
The 250 lb. NGT 18 is mounted on a 2' x 2' cinder block 'chimney', built on a concrete foundation isolated from the floor slab of the lower room. The pier carries a ¾" steel plate cut to the shape of the equatorial mounting's feet. While it is not apparent here, at least ½" separates the pier and the steel plate from the joists and the observatory floor.