Re: [ATM] Re: Weird Foucault readings

["Bob May" <bobmay@nethere.com>]

Thanks for others that actually do the calculations of what the error band
is!
Yeppie, you get some error just from the "focus" error (quotes because a
really short FL mirror will show the shadow from dark to light in the zone,
for example) is really not that important as is the slope error across the
zone.  A 1/40th of a wave error really isn't that big when you consider that
the test is only valid to something a bit less than that!
I wonder if the real limitations are not the width of the zone as measured
on the mirror but rather the angle of the zone width as you go across the
mirror????  It seems to me that the zone count goes up as you shorten the
focal ratio and only hits a limit as the zones become small due to the
diameter of the mirror.

_______________________________________________
ATM mailing list http://www.atmlist.net/