Re: [ATM] Figuring help for Lutfu

["lütfü" "çakmak" <lutfu_cakmak@yahoo.com>]

Hello Jerry,

Jim, Mitchell, Mike, Bob very thanks all of you. Very
thanks for your advising and comments. 

I understand now it's time to make a foucault tester.
But, unfortunately I don't know how is made it and
foucault testing how is done. First of all, I should
search on the internet and some other source.

Yes Jerry, I don't need to cross a continent and swim
the ocean. Already I have a micrometer for measuring
sagitta. I can use it or instead a screw as you
mentioned.

Best regards,

Lutfu
 
--- Jerry <wa4guu@verizon.net> wrote:

> Hello Lütfü
> 
> Well... there have been a few suggestions on how to
> get that sphere and good
> edge. I hope there will be more.
> 
> And more mention of a Foucault tester. I'm sure you
> wouldn't need to cross a
> continent and swim the ocean to get find a
> micrometer or dial indicator. I'm
> sure you have some source for such things in your
> country. Even so, it does
> not have to be that complicated.
> 
> You can use a 40 thread per inch screw for a
> micrometer. About an inch of
> travel is enough for the mirrors you have mentioned
> you will be making. If
> you make a slitless tester, the total movement from
> center zone to edge zone
> in Foucault testing the mirror will be about 3 turns
> of the screw. 6 turns
> if the light source is fixed and only the knife
> moves. One turn of the screw
> will be .025" of movement. You can put a knob on the
> screw and calibrate it
> into 25 divisions around the circumference to
> represent .001" per division.
> Plenty accurate for your purposes and cheaper.
> 
> The important thing in making a good tester is a
> smooth straight movement
> and solid enough that turning the screw to adjust
> the knife does not move
> the tester except for the movement made by turning
> the screw. You will want
> a stable stand for the tester and the mirror. Then
> you want a good still
> place to set it up and test. Your Ronchi images
> indicate to me that you have
> a suitable place to test. 
> 
> Make it so you can get your good eye up to the knife
> without bumping your
> nose into the tester. Maybe they have updated the
> design since, but the last
> time I looked at it the Stellafane tester was not
> designed for use by a
> person with a face. It has been a few years, I'm
> sure someone would have
> mentioned that to them by now.
> 
> The knife does not have to be razor sharp. If you
> use a razor blade, it can
> be dulled by grinding it several strokes on a piece
> of flat window glass
> with some very fine grit. Hold the blade nearly at a
> 90 degree angle to the
> glass.
> 
> Jerry  
> 
> 
> 
> 
> 



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