Liquid Telescope Mirror

Liquid Telescope Mirror

A liquid parabolic mirror which has a continuously adjustable focal length.
Proposed by Steve Hines during the second year of college.


      When a liquid is rotated on a vertical axis, gravity and centrifugal force combine to create a parabolic surface.  This technique of spinning a reflective liquid, like mercury or the less toxic gallium-indium-tin alloy, provides a surface suitable for a mirror telescope.
      Not only does this technique create a surface which can save time in grinding and aluminizing a glass mirror, the focal length of this parabolic mirror is adjustable, and can be implemented at a large size.  In use, gallium-indium-tin alloy, which remains liquid above -4°F, is poured into a cylindrical container, open at the top.  The container is rotated by a motor at a uniform speed to provide the desired focal length.  Surface tension provides a perfectly specular surface without grinding or polishing as is required of a glass mirror.
Longer (FL) 
Shorter (FL)

      As the rotational speed increases, the focal length decreases.  This series of photographs documents the proof-of-concept mock up using a variable-speed record player supporting water which was sprayed silver for the photographs.

      This is a proposal to allow the creation of large telescopes to avoid the cost, weight and fragility of a glass mirror, and to provide adjustable focal length by changing the rotational speed.  The prime mirror can simply be poured into the cylindrical container and rotated to achieve the desired parabolic curve and focal length.  This is classic mirror-telescope design plus a an additional large flat mirror, mounted above the rotating mirror, on a gimbal so that it can be turned to face the object of interest.


      This product is not for sale.  Do not contact us to purchase this product.  This project is shown only as an example of past concepts.  HinesLab currently offers consulting in the area of engineering design, photographic equipment design, as well as a variety of licensable technology.

Glendale, California, USA