Spin casting is a technique for constructing large
parabolic mirrors by using the curved surface formed by a rotating liquid (e.g. in a
rotating furnace).
It is distinct from the
spin casting
Spin or spinning most often refers to:
* Spin (physics) or particle spin, a fundamental property of elementary particles
* Spin quantum number, a number which defines the value of a particle's spin
* Spinning (textiles), the creation of yarn or thr ...
or centrifugal rubber mold casting (CRMC) technique used for casting metal or plastics.
Pioneered by
Roger Angel at the
Steward Observatory
Steward Observatory is the research arm of the Department of Astronomy at the University of Arizona (UArizona). Its offices are located on the UArizona campus in Tucson, Arizona (US). Established in 1916, the first telescope and building were ...
's mirror lab, this makes large () thin parabolic mirrors by spinning the oven as the glass is melted and cooled.
The term is applied to the fabrication of large
telescope
A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...
mirrors, where the natural
paraboloid
In geometry, a paraboloid is a quadric surface that has exactly one axial symmetry, axis of symmetry and no central symmetry, center of symmetry. The term "paraboloid" is derived from parabola, which refers to a conic section that has a similar p ...
curve followed by the molten glass greatly reduces the amount of grinding required. Rather than being cast by pouring glass into a mold (with top and bottom), an entire turntable containing the peripheral mold, and the back pattern (a honeycomb pattern to lighten the finished product) is contained within a furnace and charged with the glass material used. The assembly (or
rotating furnace) is then heated while spun at slow speed until the glass is liquid, then gradually cooled over a period of months.
See also
* technique
*
References
Bibliography
* Goble, L. W., et al. "Spincasting of a 3.5-m diameter f/1.75 mirror blank in borosilicate glass." Advances in Fabrication and Metrology for Optics and Large Optics. Vol. 966. International Society for Optics and Photonics, 1989.
* Hill, J. M., and J. R. P. Angel.
The Casting of the 6.5 m Borosilicate Mirror for the MMT Conversion. European Southern Observatory Conference and Workshop Proceedings. Vol. 42. 1992.
External links
Optical Fabrication in the Large p. 6
*
ttp://www.math.udel.edu/~pelesko/PBLOG/Team_3_spin_017.pdf An investigation into the spin casting processA Telescope Made of Moondustincluding a citation to 1966!
Wonderings On Spin Casting Parabolic Mirrors
Telescopes
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