"AGUSTIN GASPARINI" <teveotron@...> wrote:
Respect the thickness of the glass, in the front, it
is about 12 milimeters (1/2 inch).
The size of the front of the screen, as you know, the
usual crt(cathode ray tube) are from 14" to 29"
diagonal.
Also is important to consider that already has a
concave shape in the inside.
12 millimeters (1/2 inch) is pretty thin for any sizable mirror. You might
get away with it for a small mirror if you are careful and the glass is not
tempered (which would surprise me from the way that TV screens shatter).
Any-old concave shape is not necessarily a plus. You want the inside to be
a spherical section of a relatively large sphere before you are done with
grinding.
Radius of curvature is twice the focal length, so an 8in (203mm) f/6 mirror
would have an 8*6=48in (1.224m) focal length and a 96in (2.448m) radius of
curvature. The sagitta (depth of curve at center of mirror) is
approximately S=D/(16*fratio) so for said 8in f/6 mirror, we are looking for
1/12inch (2.12mm) of depth at the center. A 6in f/6 would have a 1/16in
saggita as would a 4in f/4).
One tough part may be trepanning out a small "disk" to work on. Then you
will need to figure out how to work with a blank that has a convex bottom.
(Perhaps the lens makers out there can jump in?)
It sounds like it might be a fun experiment if you have the time and are not
heavily invested in it working out.
Jeff
