From: "Thomas Janstrom" 
To: "hermit" 
Cc: "atm" 
Reply-To: "Thomas Janstrom" 


I was always tought that if something was described as *oidal then it was
like * but not quite. So acordingly a parabolic surface is like a 3D
parabola, and a paraboidal surface is like a 3D parabola but not quite say
1/2 wave from perfect. I only give this number because we need a line in
the sand. If we regard a 1/10 wave surface as finished then this would be
the correct usage of the word. Hope this makes sense.

Clear skies, Thomas
http://www.tjanstrom.com
"Don't make me set the laser printer to stun"

----- Original Message -----
From: "hermit" 
Cc: 
Sent: Wednesday, February 19, 2003 5:44 PM Subject: Re: ATM Spelling...


>
> http://dictionary.reference.com/search?q=parabola&r=2
> http://dictionary.reference.com/search?q=parabolic&r=2
> http://dictionary.reference.com/search?q=paraboloidal
>
>
> If you do a Foucault test, you are using a small sample, and you are
> more accureatly testing for a parabola and assuming/hoping it is a
> representative sample.
>
> Parabolic is the shape you get when you revolve the parabola around an
> axis.  That would seem to define the surface we hope our mirror is when
> done.  I know when I did stage hand work we had lights that were called
> "parabolic reflectors".
>
> Not quite sure what the definition of paraboloidal describes.
>
> "A surface having parabolic sections parallel to a single coordinate
> axis and elliptic sections perpendicular to that axis"
>
> Of course it is 3 am local time and my abstract thinking is worse for
> the wear.
>
> Ken
>
> "Bill T." wrote:
> >
> > >I've heard this one before but "parabolic" is
correct. And so is
> > >"paraboloid".
> >
> > Look, "parabolic" is OK for talking about sliced up
dunce caps, but
> > something as wonderful and perverse as the surface of a telescope mirror
> > deserves something a little better, for instance "paraboloidal."
> >
> > Now I've got you!  Texereau, page 17, 6th line up from the bottom.
Hah!!!
> >
> > Bill T.
> >
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>

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