[ATM] The best time to Foucault?

["jamoore47" <JohnMoore47@mail2web.net>]

HI my friends,
 
[NOTE>these tips are geared for a person whom has made a least
one "Pilot-mirror"]
AHHHH, When to Foucault?,, or;
"When should I start using that cool-looking tester!, I was
told to make?"[the beginner scratching his head].
You will get varied opinions on this Grasshopper!,
 
Here's my take on it;[IMHO].; 
[[This is just my technique on using the tester, there are many others,
that are just as effective!!]].
The best time [IMHO] to start using that "Funny-looking" fancy 
souped-up-"razor-carier", is right after "the what I call the 1st-polishing- stage"
I polish in 2-stages;
pre-polish, and final polish.
Pre-polish is what some refer to as a "Flash-polish", you can use pads,
abrassives,or a plastic-screen.
 
NOW, this next tip 2-tips are very important!
 
1. you actually use your tester in 2-stages, or in other words
 you use it for 2-different reasons! The first-stage is after
 "pre-polishing", to check for "astigmatism, Overall figure of
 the optic[ie.,roughness of figure(primary and secondary ripple),
astigmatism, and the dreaded "TDE"(turned-down-edge). 
This is also a good time also to start practicing the use of a "Ronchi-screen"
with your tester!
 
NOTE; during this stage (stage 1) its very important to understand you
"ARE-NOT testing for the accuracy of your parabola!,[ie., taking readings],
you are only testing for "general-figure-abnormalities!"
 
2.  At stage-2, [and again we are-NOT taking readings!], you are looking for, 
and correcting-for,[I also call this stage the Correcting-Stage]  any abnormalities in 
"figure-of revolution", Bad-Zones!
At this stage the BEHAVIOR of the Pitch becomes Vitally-Important!,
Pitch is a "Vicious-Fluid" like glass, only softer, with varying degrees of hardness!
PS;Think of glass as an "Ice-cube", and you will have an Idea what glass
actually is like.
[you must to the best-of your ability;
Control; Room-temp;humidity;and Pitch-temper!]
 
After these 2-stages are completed to the best of your ability!,
Then you can proceed to "Figuring", which has NOTHING at all
to do with Polishing!, That's when you use your "Tester, to take Readings!"
 
PS;
There are many wonderful people here on this forum, with different
Optical-techniques, and they ALL WORK!, so don't let that confuse-you!,
in our atm-world, there are lots of roads to Rhome!
 
Good-luck with your Optic, and don't settle for nothing but the best!
and you will end-up with an Optic that is;
"Beyond Reproach!"
 
PSS; I Hope these tips help you out,and All [Friendly]comments are welcome.
[Im very-humble, and I own a "Industrial-grade Flame-suite!,he,,he].
 
Clear skies, and God Bless to all!!
 
John Moore.
atm since 1974.
_______________________________________________
ATM mailing list http://www.atmlist.net/