ATM re: exchange rate -Reply

[BRYAN LEENHEER <BLEENHEE@millersqa.com>]

>Since you are all reading this, I remember an article I once
>read on spinning mirrors I think it was mercury or
>something. Couldn't someone spin molten glass to shape a
>mirror, or is this done already?

Regarding the spun mirrors...  They are indeed Hg, with a
coating of oil to keep it from oxidizing.  They can only be
used to observe at and around the zenith, though.  

Spinning glass, though... I think this isn't done because the
parabola would be ground out during polishing, but I can also
come up with some nasty ideas about uneven cooling,
cooling too fast, and high velocities.  Could also be because
of the variables involved.  The viscosity of the glass changes
as the heat increases/decreases, and the velocity has to be
just right to get the appropriate parabola.  Took a long time to
figure out the right speed to spin the mercury, and I'm not
sure if the numbers for glass exist.  Maybe someone out
there wants to do a little research and find out?

Bryan