Re: Re[4]: [ATM] On Axis Foucault (try this instead)

["David Harbour" <scarab2@cox.net>]

I'm glad you asked, Richard.

Somewhere (I know who can do it) there is someone who can help us make this
into a test that will prevent you from having to test from center of
curvature. The problem for you, with these teeny tiny optics, is how bulky,
vertically or horizontally, your test apparatus is going to be, if you use
my popular Foucault with one half of the razor the knife edge offset
(extended from the slit); you see, in this case, there will be a separate
problem not encountered with a larger mirror: the degree of offset of both
the slit and the K.E. will be considerable, and there will be potential
negative effects for other reasons. My "half-witted" idea was this: set up a
very high quality collimator (the 6" lens I sold would have been perfect-
sorry). But a good quality paraboloid of any size (bigger than the dinky
mirror) would work well. Set it up as a collimator (OFFSET YOUR LITTLE
MIRROR; DO NOT INCLUDE THE LIGHT SOURCE IN THE BEAM)- make a very tiny light
source for it, make sure that that light source is in EXACTLY the infinity
focus for the mirror, and shine it at your little tiny piece of glass. Now,
the only challenge here is, (of course, you will have a tiny diagonal in the
light beam of your collimator-avoid it, as I have suggested; off set the OTA
of your collimator)- is to know the right (and I am sure, VERY simple math
required to measure zones on your little spherical mirror; i.e., you will
need math that is the INVERSE of: "d equals r squared over 2R"):

http://www.atmsite.org/contrib/Harbour/Foucault.html

I may be a little confused here, but it seems to me, intuitively, that if
one can do something "forewards", they can do it "backwards". You would have
to make a tiny mask and measure zones!

Get the Flying Wing Man to do the math for you! He will love it; his ego
will love it; besides, he is one of the brightest (at math) on the list.

That's my crazy, idiot idea, Richard. I think it would work. Where you would
get that tiny prim or diagonal is beyond me.

Dave


----- Original Message ----- 
From: "Richard" <cnc@cncservo.co.uk>
To: "David Harbour" <scarab2@cox.net>
Sent: Monday, June 20, 2005 7:26 AM
Subject: Re[4]: [ATM] On Axis Foucault (try this instead)


> Hi David,
>
> Sunday, June 19, 2005, 6:55:34 PM, you wrote:
>
> DH> "KISS"
>
> Indeed, keep it simple. Did your idea not come to anything?
>
> -- 
>
> Best regards,
>   Richard in the UK
>
>
>
>


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