[ATM] Figuring with sub diameter lap

[BMARRIOTT at pacbell.net (Bill Marriott)]

Jonathan;

In regards to your 4+" lap you are using on your 8"f5. Over at
the Chabot Telescope Workshop, we usually recomend using a full
size lap on smaller mirrors, as it is pretty easy to manipulate
the lap into working areas of the mirror as needed, with out the
issues of curve smoothness (zoning) or surface roughness (dog
biscuit..arf arf!) that one may see using a subdiameter lap. And
when the need arises to use a SDL, it is also good to have a full
size lap to smooth out the work previously done.

That being said, it in no way means that you won't be successful,
so dive in and see what happens, and report back. 

Regards

Bill Marriott
Woodacre, Ca.
USA