Yes,, BUT,,
it may be good enough for a low sreq radio signal, but in this casting they still had to make the reflecting surface the same old way, grinding with grits, to even out the surface,, then polish it, then paraboloze it.
all the spin casting does it take the "Rough Grinding" portion out of the process, since 90%+ of the concave shape is raedy.
But as is, it's still no where near as accurate as it needs to be for optical work.
Radio, maybe,, optical nope.
mvm wrote:
Joe,
??
As you surely can see this is an example of rotation casting. In this case of a large mirror.
Joe schreef:
And your point is?
mvm wrote:
http://medusa.as.arizona.edu/lbto/tech/mirror.htm
Greg D. schreef:
Best "form" is probably not to have one. Wasn't there a post recently talking about making a mirror by spinning casting resin in a shallow round dish? Perhaps a good use for that old record (*) player gathering dust in the garage...
Greg KO6TH
(*) an ancient mechanical instrument for storing music in an analog form
Date: Thu, 14 Aug 2008 15:59:26 -0400 From: ka2pbt@arrl.net To: amsat-bb@amsat.org Subject: [amsat-bb] Re: DIY: Parabolic mirror
agree ..... what would be a good form to start with rather than the bottom of some random water tank??
Assuming you had a proper form ... I think the construction process has merit.
The next step would be to coat the fiberglass shell with something metallic ... foil ... screen ????
On Thu, Aug 14, 2008 at 2:04 PM, Franklin Antonio wrote:
At 07:34 AM 8/14/2008, Joe wrote:
> Too bad it's not parabolic, and probably far from even spherical. > >
Precisely. Apparently the author thinks "parabolic" just means some kinda symmetrical concave surface.
This guy obviously isn't an antenna guy.
I've found Make magazine to be a crock in general. Too bad.
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