Re: ATM Mirror-Making Kit Proof Of Principle

[epabcc@epa.ericsson.se (Bratislav Curcic)]

Val Germann wrote :

> take all the
> way through polishing without any real testing,
> using polishing pads rather than a pitch lap

Hmm... the pads are OK, but I would never finish a mirror
intended for visual use just with pads. The amount of ripple is
far greater than with pitch. Also, inability of the lap to conform 
to the mirror may introduce serious zones (if one pad was thicker
for some reason for example). It needs but 15 minutes of smoothing
to significantly "clean up" the surface.

> may, if he MUST, dispense with all testing

Yes, this is true, but do not forget that marginal spherical mirrors
do not allow for ANY error towards the oblate at all; you may have a
hole in the middle for example (and it will make your mirror look even 
better), but central bulge will push it way outside acceptable.
Point is - testing a sphere is so easy that simply doesn't make sense
NOT doing it.
If you REALLY want to make mirror without testing - make it longer than
"minimal" f#. This gives you more room for errors.

Good luck, and tell us about results !

Bratislav