Explanation:

Liquid-Mirror Telescope is a novel instrument that employs a 4-meter-diameter rotating mirror made up of a thin film of liquid mercury to collect and focus light. Scientists spun a pool of mercury which is a reflective liquid, so that the surface curved into a parabolic shape which is ideal for focusing light. A thin transparent film of mylar protects the mercury from wind. The reflected light passes through a sophisticated multi-lens optical corrector that produces sharp images over a wide field of view. A large-format electronic camera located at the focus records the images. The rotation of the earth causes the images to drift across the camera, but this motion is compensated electronically by the camera. This mode of operation increases observing efficiency and makes the telescope particularly sensitive to faint and diffuse objects.