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

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

Yep, that's the stuff good testers are made of.  Not to say that
you have to go that heavy and solid for a single mirror but that
is the way to go for more "production" work where a group is
doing the testing.
My setup right now is in a shed which is attached to a garage
wall.  The test stand is on a tabletop attached to that wood wall
and has legs every 8' or so to hold up the table.  All kinds of
things get put on that table and it helps to tend to keep things
from moving about.  The head is pretty stationary with nothing
more than a lip over the edge of the table to keep it aligned to
the system.  The mirror stand runs on a piece of metal, really a
bit of the shelf hanging stuff that you can get for hanging
bookshelves on the apartment wall, and the mirror stand has two
pulley shaped wheels that ride on one of the edges sticking up
(the shelf hanging stuff is mounted upside down with the legs
sticking up) and a roller on the other side.  The tabletop is
fairly flat and care was taken at the joints to insure that it is
flat enough to roll over.
Right now, I'm considering motorizing the mirror support so that
it will move in/out, sideways and up/down so that you don't need
to go back to it to do adjusting to get the finder LED return to
the right spot.  It's kind of a pain when you need to move the
mirror a little bit so that it is properly centered on the
camera!
Bob May

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

----- Original Message -----
From: David Harbour <stainless_steel@suddenlink.net>
To: Bob May <rmay@nethere.com>; <atm@atmlist.net>
Sent: Friday, May 30, 2008 4:05 AM
Subject: Re: [ATM] Mirror cell ramblings re: thin plate
glass3/4-inchx24-inch


> Bob, Dale, and all:
>
> I briefly, quickly searched my archives of articles and found
my article,
> with four hand drawn (very well, I should tell you) of my
"Giant Measuring
> Engine" for mirror testing. There are four very clear
illustrations in it.
> Now: what does this have to do with the current thread?
>
> Just this: mirror and tester were always connected with 4,500
lbs of masonry
> walls, on which were the rails for the testing table trolley.
The distance
> between the mirror, and the test set up (whether Foucault or
Caustic- I
> eschew interferomtry, being from the old school, and believe
Irwin Schroeder
> when he says one can measure accurately enough with caustic,
that after
> reducing the data with the formulae, one can easily come up
with an
> accurately inferred wavefront of up to one fiftieth of a wave)-
however, I
> am thinking of you guys- this "optical bench" would not allow
the distance
> between mirror and test set up to change. If I am not mistaken,
that is what
> your debate is about.
>
> The "guide rail" for the trolley was arrow straight, and
perfectly round; it
> had to meet these criteria to do what it originally did: go up
and down
> through a sleeve, or sleeves, to suck oil out of the earth.
That is why they
> call it "sucker rod"- I used it for the kinematically arranged
> bearing/wheels for the guide rail, and it performed
beautifully. They
> trolley would not "run out" laterally, by even a thousandth of
an inch.
> "Sucker Rod" (was- probably still is) available in diameters
between one and
> three quarters up to 2 and three quarters of an inch in
diameter, and was
> only pennies per foot. Almost as hard as diamonds; will make
the older
> machinists curse when they try to part and face it.
>
> If stacking up (no mortar is necessary) about 140 concrete
blocks frightens
> you, intimidates you, then don't ask for the article. A cheapie
plastic
> level, 48" length, and some stuff to shim the blocks with (a
big jar of
> coins is handy) made the jop delightfully easy. Of course, a
garage or a
> basement is handy. When you get ready to move up into that
dream house, or
> down into that pup tent, because of the coming great
depression, it is very
> easy to just take the blocks apart. They are not glued
together.
>
> You are wondering: "All that sand!!!! He must have scratched a
lot of
> mirrors!!!! As I told you all, individually and severally,
before, I NEVER,
> EVER, scratched a mirror that I ground, (or polished) after my
first eight
> inch. I've already conveyed to you the secret of how to keep
sand from
> getting between tool and mirror, and it goes for concrete
blocks. Leave the
> loosely bonded sand lying where it is; do not caress the blocks
with your
> hands, while working a mirror. Gravity will keep the loser
surface sand
> pieces where they are. And, with the design of the bench, they
are way below
> the level of the trolley, which rides on guide/outrigger, well
above the top
> of the block walls.
>
> Ask for the article. It is an HTML email, illustrated, and all
I have to do
> is forward it. Kind of a miracle, that I have it on the new
machine; three
> previous machines I had melted down, that that article was on.
But I back up
> my files.
>
> "FORTUNE FAVORS THE BOLD"
> (and the innovators)
>
> R-101/
> Col. Vincent Richmond/
> Davey/
>
>
> ----- Original Message -----
> From: "Bob May" <rmay@nethere.com>
> To: <atm@atmlist.net>
> Sent: Thursday, May 29, 2008 3:55 PM
> Subject: Re: [ATM] Mirror cell ramblings re: thin plate
> glass3/4-inchx24-inch
>
>
> >I have trouble doing the Foucault test on benches and
> > interfrometry is even worse for vibrations.
> > Then again, if the seperate parts are sturdy enough, you can
get
> > away with it.  I also note that you mention using fast
shutter
> > speeds to get the vibrations out of the interfrograms tho so
you
> > do have some problem with vibrations.  It does help tho to
have
> > nobody walking about vibrating the floor.
> > Bob May
> >
> > rmay at nethere.com
> > http: slash /nav.to slash bobmay
> > http: slash /bobmay dot astronomy.net
> >
> > ----- Original Message -----
> > From: Dale Eason <atmpob@yahoo.com>
> > To: <atm@atmlist.net>
> > Sent: Wednesday, May 28, 2008 2:33 PM
> > Subject: Re: [ATM] Mirror cell ramblings re: thin plate
> > glass3/4-inchx24-inch
> >
> >
> >> Sorry Bob but I have to take exception to that
> >> generalized statment.  I use two tables and it works
> >> very well. Actually a table and a tripod.  I have also
> >> taken Igrams on the second floor of a building and was
> >> successful because I used a fast shutter to stop the
> >> vibration.
> >>
> >> However air current induced see is much more of a
> >> problem but that is taken care of by averaging many
> >> analysis sets.
> >>
> >> There are usually ways to address all of the issues.
> >>
> >>
> >> Dale Eason
> >>
> >> --- Bob May <rmay@nethere.com> wrote:
> >>
> >> >  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.
> >>
> >>
> >>
> >>
> >> _______________________________________________
> >> ATM mailing list http://www.atmlist.net/
> >>
> >
> > _______________________________________________
> > ATM mailing list http://www.atmlist.net/
> >
>
>
>

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