Qty 1, of roof peak octagon 8-way spider bracket. Qty 40, of 1/4" x 1-1/2" lag screws. Roof rafters' pitch angle is fixed at 21.5-degrees, close to 4-12 pitch. Roof rafters and cross-tie beam lumber to be kiln dried lumber pine, cedar, redwood, etc.
Roof rafters' size to be 2x6 for octagon widths up to 14 feet and 2x8 for widths more than 14 feet. Cross-tie support beams are required every 24 between adjacent rafters to support roof deck plywood/osb boards and to support snowloads.