Wooden Towers

2-60. Wooden Towers. When it becomes necessary to raise the line of sight to clear obstructions on

longer lines, a stable tower must be built. It is necessary to construct an instrument stand and a separate

platform to support the observer. The whole structure is referred to as a tower. Wooden towers are built

at the station, using lumber or natural forest materials.

a. Towers should range between 6 and 25 feet high. It is not considered practical to build wooden

towers higher than 25 feet. When greater heights are needed, aluminum or steel towers are used. The

materials normally on hand and the easiest to handle are 2-inch x 4-inch x 16-foot, 1-inch x 4-inch x 16-

foot, and 1-inch x 12-inch x 16-foot boards. For towers over 15 feet, 2-inch x 4-inch boards are usually

doubled on the lower two-thirds or so of the tower's legs. The inner or instrument tower is built as a

tripod, usually completed on the ground and set up in leg holes as one piece. The scaffold supporting

the observer's platform is usually four legged, with two opposite sides put together on the ground and

stood up around the tripod. All legs are laid out and marked on the ground. One side each of the tripod

and the scaffold is used as a pattern to cut the horizontal ties and diagonals the same for all sides. The

instrument tripod is not guyed during observation, but it may be weighted with rocks or other weights to

increase its stability. In higher order work, no observations should be made on higher wooden towers

during extremely high winds. However, the instrument tripod may be guyed when not in use to prevent

damage from high winds.

b. The outer tower must be strong enough to be safe and must not touch the inner tower at any

point. It should be provided with hand railings, as an observer often loses his sense of balance

momentarily when taking his eyes away from the telescope. If necessary, the outer tower should be

guy-wired at all four corners.

EN0593

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