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

["Jerry" <wa4guu@verizon.net>]

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

-----Original Message-----
From: Norm Prince
 
Thanks a ton yall for all the great words of wisdom...the polishing is 
moving forward...

To be sure I wasn't concerned with the notions of figuring just yet...just 
wanted to know how to, if necessary, to try to work it back to a more 
spherical shape as i went...the focault and ronchi shadows are the only way 
i know to see if i have anything like the desired sphere.  I wasn't sure if 
the lack of sphereocity would shoot me in the foot as i kept on 
polishing...it would really suck to have to back track at this point.

So thanks again ...yall are the greatest.  Lending your know-how to folks 
like me with very few intellectual resources.

-norm prince-
Georgia, USA 


_______________________________________________
ATM mailing list http://www.atmlist.net/

_______________________________________________
ATM mailing list http://www.atmlist.net/