Editing Parabolic reflector (section)

===Scheffler reflector===
The focus-balanced configuration (see above) requires the depth of the reflector dish to be greater than its focal length, so the focus is within the dish. This can lead to the focus being difficult to access. An alternative approach is exemplified by the '''Scheffler reflector''', named after its inventor, [[Wolfgang Scheffler (inventor)|Wolfgang Scheffler]]. This is a paraboloidal mirror which is rotated about axes that pass through its centre of mass, but this does not coincide with the focus, which is outside the dish. If the reflector were a rigid paraboloid, the focus would move as the dish turns. To avoid this, the reflector is flexible, and is bent as it rotates so as to keep the focus stationary. Ideally, the reflector would be exactly paraboloidal at all times. In practice, this cannot be achieved exactly, so the Scheffler reflector is not suitable for purposes that require high accuracy. It is used in applications such as [[Solar cooker#Paraboloidal reflectors|solar cooking]], where sunlight has to be focused well enough to strike a cooking pot, but not to an exact point.<ref>{{cite web| url=http://www.solare-bruecke.org/index.php?option=com_content&view=article&id=2&Itemid=2&lang=en|title=The Scheffler-Reflector | last=Administrator|website=www.solare-bruecke.org}}</ref>