Re: ATM Cooking a paraboloid

[Dwight Elvey <elvey@hal.com>]

"Arjan te Marvelde (ELN)" <Arjan.te.Marvelde@eln.ericsson.se> wrote:
> 
> Hi,
> 
> Some time ago i saw a documentary about an artist making vases out of glass.
> The way he did this was by heating a piece of thick glass, supported by a
> circular aperture, in a kiln. At some point the glass starts sagging down
> through the aperture, eventually forming a vase shape.
> 
> So i wondered: what happens if you stop the sagging when the glass reaches the
> right sagitta. Would the shape be close enough to a paraboloid to require only
> some additional figuring?
> Maybe this is an alternative to slumping?
> 
> 
> /Arjan te Marvelde


Hi Arjan
 Although not quite the same but blanks for large telescopes
are spin case. The surface is a parabolic that has the focal
length controlled by the speed. Regrettably, the quality of the
finished surface is not to the level required for a telescope.
 Kiln slumping is done in a form to keep it close to the right
shape. Glass just doesn't come out smooth enough to be used
at visual wave lengths from any melting process.
Dwight