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The polar shaft for the 140-foot (43-meter) telescope in Green Bank, West Virginia is one of two axes for our 200-foot tall telescope. This shaft is a machined, 3.5% nickel steel casting weighing 40 tons, welded to a tubular, rolled plate straight section weighing 90 tons, which in turn is welded to a 3.5% nickel conical transition casting machined to 85 tons. The maximum length is 55 feet and diameter is 12 feet. The world’s largest metal bearing (covered) was bolted to the end using 29 5-inch diameter high strength steel bolts to become the rotational bearing for the telescope. It took six hours to carefully lift and place this 555-ton shaft into its casing on the concrete pedestal.

The unique 140-foot (43-meter) telescope shines on a clear night in Green Bank, West Virginia in 1975.

The Big Dipper points to the 140-foot (43-meter) aluminum-clad parabolic dish antenna of the world’s largest polar-aligned telescope. The rounded yoke swivels around the central axis of the telescope which is aligned perfectly with the rotational axis of the Earth. For the Northern Hemisphere, that means that the sky (and this telescope) wheels around a point near the North Star, Polaris. In this way, the telescope can easily track objects in the sky as they appear to rise and set from the Earth’s spin on its axis.

The 140-foot telescope in Green Bank, West Virginia is the largest equatorially-mounted telescope in the world. That means that it moves on a gear parallel to the equator of the Earth because it spins on an axis aligned to that of the Earth. In this photo, its two axes of motion are in view. The first is the giant white semi-circular tube with just-visible toothy gears around its edge. This gear is driven by the polar shaft which is aligned to the axis of the Earth. When the Earth turns, this axis turns in the opposite way, to keep the telescope tracked on the sky. The tilting gear is the wedge shape under the 43-meter dish’s support structure.

The unique 140-foot telescope in Green Bank, West Virginia stands 200 feet tall. It took six years to design and construct, and then took the astronomical world by storm in its discoveries of organic molecules in space. A 140-foot (43-meter) aluminum-clad parabolic dish antenna sits on the world’s largest polar-aligned mount. The rounded yoke swivels around the central axis of the telescope which is aligned perfectly with the rotational axes of the Earth. In this way, the telescope can easily track objects in the sky as they appear to rise and set from the Earth’s spin on its axis.

The unique 140-foot telescope in Green Bank, West Virginia stands 200 feet tall. It took six years to design and construct, and then took the astronomical world by storm in its discoveries of organic molecules in space. This telescope is still operating, but under a more modern name of the 43-meter.