Re: [ATM] Mirror cell ramblings re: thin plate glass3/4-inchx24-inch

["Bob May" <rmay@nethere.com>]

Ted, Foucault testers are easy to build.  Build one on the cheap
and play with it.  The Stellafance version is a nice tester and
also is quite a good one.  Go find a TV camera of the little
security type and replace the lens with a longer FL lens - a
simple lens in a hole in a box will do fine as the light is only
a single color and thus you don't need to have color correction
nor a wide field.
Ronchi gratings of excellent quality are available from WillBell
for very cheap.  Get one or two!  Make an eyepiece with a grating
instead of glass and that will do very nicely for testing with a
star.
Ineterfrometers are a little bit more difficult but they are not
that hard.  The biggest problem with them is that there is little
indication that you're getting close to getting fringes if you
are very far off from getting them.  Once you find the fringes,
it will become a lot easier.  I'll also note that you do need to
have a stable support for the system - no doing the work with the
interfrometer on one table and the mirror on another table.
Better is to just do it on a solid concrete floor that is on the
ground.  Second floor concrete will tend to shake too much in
most places.
BTW, heavy isn't necessarily stable!
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net

----- Original Message -----
From: Ted Cohen <tcohen@blakeglobal.com>
To: <atm@atmlist.net>
Sent: Tuesday, May 27, 2008 10:53 PM
Subject: Re: [ATM] Mirror cell ramblings re: thin plate
glass3/4-inchx24-inch


> Dale,
>
> My efforts to date in the metrology area are lacking sufficient
precision,
> and I probably need  to give up on that project and try to
procure the
> necessary Foucault and Ronchi testers (as already suggested by
several
> posters). I have no experience in this area. Since I'm going to
polish with
> the glass in the cell, I was planning on using star testing as
a fall-back
> in case my laser metrology technique fails. But I appreciate
what you're
> saying Dale, it would be nice to be able to share my progress
(or lack of
> thereof) by using the traditional techniques, something
everyone can relate
> to.
>
> Ted.
>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
>

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