What is Rotating furnace?
A '''rotating furnace''' is a special type of [[furnace]] used to make [[Lens (optics)|lenses]] or [[mirror]]s for [[telescope]]s.<ref>{{cite web |url= http://www.industrialmetalcastings.com/foundries_rotating_furnace.html |title=Rotating Furnace|first= |last=|work=industrialmetalcastings.com |year=2011 |accessdate=12 October 2011}}</ref> [[Glass]] is placed in the furnace which is then spun up and heated. The top surface of the melted glass takes on a [[wikt:concave|concave]] shape. The glass is cooled while still spinning. The spinning makes the glass the same shape as the main mirror used in a telescope. [[Computer]] controlled grinding machines can correct the shape of the glass. The concave top surface can be coated with silver and be used as a focusing mirror. The shape of bottom surface is made by the container the glass was melted in. The technology is being used for the [[Giant Magellan Telescope]]'s seven mirrors. Large focusing mirrors can also be made using liquid [[mercury (element)|mercury]], such as the [[Large Zenith Telescope]]. The rotation is continuous and the metal remains liquid; once all waves and imbalances die out, the telescope is then used. ==References== {{reflist}} {{science-stub}} [[Category:Telescopes]] [[Category:Optics]]