- The depth of glass to be removed, e depends on the focal length
- so for a 6" dia (r =3 inches) 48 inch focal length mirror.
- 3x3/96=.0468 inch
- Note R=2x the focal length, 48x2= 96 inch
rxr/2xR= e
r = useful mirror radius
R= Radius of curvature of mirror