From: "Richard Schwartz" 
To: 
Reply-To: "Richard Schwartz" 


Jim,

Your use of the word "glue" to describe RTV silicone shows your
GROSS INGORENCE of silicone's physical qualities.  You should send an
immediate letter of apology to General Elecric, the makers of GE-II
silicone bath tub sealer.

It seems to me that optical quality is independent of the means used to
mount a mirror or the use of silicone somewhere in the telescope not
related to the optics.  If you make a silicone cell for a crappy mirror,
you still have a crappy mirror.  Consider the following:

1. What "glue" is pliable when it dries, enabling it to be used
as a compliant bearing, a thermal stress isolator, a spring, a shock
isolator, and a million other purposes where an elastomer is called for? 2.
What "glue" holds up at 400 degF? 3. What "glue" bonds
well to glass, wood, and metal for 32 years and still holding strongly? 
(OK, bonding to wood is meaningless at 400 degrees F, and the example is a
sample size of 1.  I would do another test,  but I probably don't have 32
years left in me..)
4. What "glue" is virtually indestructable, waterproof when cured
and immune to attack by most common organic solvents (acetone, MEK,
turpentine, alchohols, napthas, etc.)
5. What "glue" is an excellent heat conductor? 6. What
"glue" is cheap and commonly available at any hardware store? 7.
What "glue" is also a semiconductor? 8. What "glue" is
totally uninteresting as a nutrient to hungry creatures, great and
microscopic?

[note that silicone can also be used as glue in some applications.]

Some glues may have some of these characteristics,  but RTV silicone has
ALL of these characteristics.  In my engineering practice, I find it to be
a wonderful material almost as precious and versatile as glass, a rich
source of ideas for inventions that are to weird for the orthodox believers
to contemplate.   Too bad I can't grind, polish, or aluminize it.

By now you know what I am advising you to clamp down really, really tight.

. . . Richard

----- Original Message -----
From: "J&S" 
To: 
Cc: 
Sent: Wednesday, March 12, 2003 7:20 PM Subject: ATM Style and Technique
was Large spider and secondary holder


. . .

>      There is also a third type (the Newbie). More on that later.
. . .
> C) My experiences (though mostly just observational -
> aesthetic) have tended to be negative where silicone/glue is concerned. I
> look through dozens of new amateur-made telescopes every year and see many
> that produce sloppy, soft, or astigmatic images. Some of these are obvious
> mechanical stress issues, and some could be just plain bad optics, but the
> lion's share have silicone in the mix somewhere. Hence my personal dislike
> of the stuff.

. . .

>      True, there is no qualitative science there, but from an
> aesthete/hobbyist point of view, that's all I need to disqualify it for
> personal use in applications where high contrast, high resolution imaging
> are required, preferring to use the methods I have had positive experience
> with and am most comfortable with using to achieve my best possible
result.
>      It is obvious that other folks have had the opposite experience and
> prefer the glue. No problem. We all have different experiences, skill
sets,
> and preferences in our media and methods, and that is a good thing!
>      I hope that clarifies my point that brought this:
. . .
>      I think we agree that in that case the Newbie should use the easiest
> fastest methods he can, then take his time building two or three more
> scopes, experimenting and trying different methods. Eventually, he will
> learn the methods that match his personal skill sets, tastes, and
> objectives.
>      From my perspective, it is ALL fun. As anyone that knows me will
> attest, I enjoy very much seeing the wide variety of materials and
> techniques used in telescope making even though I may not use them. For
> instance, I am a horrible woodworker, but I hold my own with metal. I
don't
> push glass anymore because it cuts into my metalworking time. But that in
no
> way means I don't appreciate a fine piece of woodwork or a tack-sharp
optic
> made with unconventional means.
>      I also enjoy seeing the progress made by those that push the
envelope,
> and you have done some GREAT envelope pushing over the last few years Tom.
I
> respect the heck out of that, even though I'm not much of an envelope
pusher
> myself (time is precious to me so I tend stick to perfecting my tried and
> trues rather than venturing outside my skill set.)
>      Keep up the good work!
>
> In Friendship,
> - Jim S.
>
>
>

--- BBBS/NT v4.00 MP