11 Dec
2000
11 Dec
'00
9:51 a.m.
Dwight Elvey <elvey(a)hal.com> wrote:
If one only looked at warping, it would only take
about
0.060 of a depression of the center to cause a 20 foot focal
length.
Oops!
Error in my calculation:
It should have been 0.005 inches.
Formula for saggitta is
r^2/4f = s
In this case r ~= 4.5/2 inches
f ~= 20 feet ( 240 inches )
go figure!
Dwight