Big Dipper and the 140-foot
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.
Credit: T. Burchell, NRAO/AUI/NSF
