Re: [ATM] fishing for a lil polishing advice!

["Norm Prince" <norman.prince@verizon.net>]

No ...no MoM...I decided i might wind up with too many centers from bad 
centering on the MoM...so i switched to the barrel at 9 AO...even then i was 
just using the MoM as a spindle really (just yanked the overarm off and used 
my hands with the turntable spinning)...quick note...the goal is a 12" f/5.

This being only my second mirror, and having learned alot doing the first 
and a lot more reading and listening since then i just wasn't sure what was 
spherical enough during the many faces of polishing...that said...i just 
can't help looking...i don't mind wasting the time...i'm in no hurry....it 
will be done when its done...i waste plenty of time on women and beer (or 
monitoring the atmlist)...so a little peek under the KE is nothing.  The 
divergence of opinions on to correct ASAP vs "forget about it"....is 
intriuging though, and i'm guessing one that can only be developed thru more 
experience...Its good to hear such a lively debate so us newbs can pick 
which ever fruits we like at the moment from the tree of knowledge, and of 
course develop our own opinions on how ripe they are.

as for the shape i see in the pictures...All i know is that the lines 
weren't straight as i understand a sphere should be...if i had to venture a 
further analysis i would say no more than it was maybe a little deeper in 
center than a sphere should be..not to mention the ant hill that seems to 
reside at center in the KE pics.

Many thanks to all yall again...gonna go polish some more ...hehe...no doubt 
I'll be trolling again after a few more hours of polishing lol....

-norm prince-
Georgia, USA

----- Original Message ----- 
From: "Jerry" <wa4guu@verizon.net>
To: "'Norm Prince'" <norman.prince@verizon.net>; <atm@atmlist.net>
Sent: Monday, May 21, 2007 17:57 PM
Subject: RE: [ATM] fishing for a lil polishing advice!



May as well add another opinion here... contrary.


You had your tester and you had a little polish on the mirror. Who could
resist taking a look. Looks neat.

Now you have done that. Don't bother looking again unless you want to waste
time that could be used polishing.

Let's see if I can start a firestorm...   Forget all you have ever heard or
read about turned down edge. It isn't caused by what you think. That would
be what you have read in books and on the web.

Having forgotten about turned down edge, you will be free to learn to
figure. You do that by correcting zones. That is the most important thing to
learn about figuring.

I think I just recently told someone... Contrary to common belief the edge
is a small area of the mirror. It is better to have a turned down edge
surrounding a smooth accurate parabola than to have a perfect edge that is
only a band around a lousy parabola.

After you learn to figure the mirror to a good parabola, then you learn to
make a good parabola and a good edge at the same time.

If you start with the edge there will be many things you can't learn about
figuring because you think they would turn the edge down.

Are you doing this on the Mirror-o-Matic? You won't be doing the W stroke
with that. I would suggest that you go to the Yahoo Torusmirrorgroup and
look in the files there for a file named Machine Figuring Stroke.doc.

Truth be told, I would have to recommend learning to figure by hand first.

By hand TOT (tool on top) a W stroke 1/2D tall and 1/3D wide will come
closer to making a sphere than the commonly recommended 1/3 tall by 1/4
wide. In any case the dimensions of the W is what you adjust to make a
sphere. If the current stroke is making an oblate you need to make the W
larger. If the curve is toward a parabola you make the W smaller.

The sphere will not be a perfect one. It does not need to be. If you wanted
a perfect sphere you will have to work for it just as you would have to work
for a perfect parabola.

What shape do you see in the test images you posted?

Have I said enough heretical comments?

Jerry 


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