[ATM] The best time to Foucault?

[Roman Toledo <rtoledo2002@yahoo.com>]

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.

*****************************************************

       John thanks for the encouragement,  I'm still in stage one,
working on 2 mirrors.  I've learned a lot so far and know there's more
to be learned.

       Right now I'm working exclusively on my second mirror since I
bought a Celestron NGPS 9.25  f/10   so I want to get a fast mirror
done.  It seems ;) I've changed my mind again and I'm back in love with
a fast mirror to supplement my viewing habits. not that I'm complaining
about the NGPS  I love it.

      I've only looked once at my second mirror and I'm not worring
about errors at this time since I'm using a full size pitch doing COC. 
I've learned that I like to polish with weights on my 3"thick tool TOT,
it allows me to push nice and slowly and make a smother pass,  so far
the edge has begun to polish out and is currently about 50% in from the
edge polished to where there is little light defraction on the edge of
the glass.

    I've been working a lot of hours and seem tired, so I'm putting 15
minutes here and there, no real hurry.  My first mirror (and my own
creation ;) )  sits there 90% polished but since it's a f/7 it's going
to wait till the fast one is done.

  I just also ordered a couple of secondaries from JC Mulherin and once
those arrive I'll work on those in the house and try make progress on
those too, I'll come back and ask about those at that time, specially
how to get them tested, but that will have to wait for now.

I was going to take advantage of all the clouds and polish, but I just
don't seem to muster the energy.  the TV won tonight.

thanks again from one beginner  and as a update to those wondering what
happened to me ;)
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