Dial indicator and air spring.

To measure the pier movements before and after the stabilizing methods were applied, and to ensure that tightening the cables did not pull the pier from its static position, I placed linear dial indicators at right angles to one another against the top of the pier attached to the structure.

It's amazing to see how much movement a house does when people move around or the wind blows. During strong winds recently, you could watch the house move 10-15 thousandths a couple of seconds before the sound of the wind picked up and then watch the house return to rest before the howl of the wind subsided. Way cool to see this happening, and serves to underscore the importance of not having the surrounding observatory structure touch the pier in any way.

Below the dial indicator is one of four Goodyear air springs.  More on this on the next page.