Re: [ATM] How to do this right

["Jerry B. Hillman" <JBHillman@ev1.net>]

Hi David,

 This is the correct link to your pictures.

http://www.atmlist.net/contrib/dwilliams1128-at-earthlink-dot-net



>But also I need to support my mirror in a better way than by just setting
and resting it up right

Okay, This is a good place to start.  If you would like, I'll send you
pictures of the mirror stand I made.  The plans are on the Stellafane web
site.

<This way would want to introduce an effect where the mirror tries to slump
over on itself.  And we don't want that.

True

<So what we need is a sleng holder like a piece of carpet that runs down and
around the bottom of the mirror to support it evenly.

You don't want to use carpet.  It isn't stable enough.  Nylon webbing works
well. ( A dog leash, at least 1" wide.  BIG DOG!!)


 <How this will work in a telescope mount where the edge of the mirror is
constantly shifting around as you look at different sky objects, I don't
know.

Actually, when the mirror cell is  properly made, the mirror will not shift
around. You would never keep the optics in alignment if it did.  Once again,
I you ask, I will send you pictures.

>Also I need a floating point mirror cell (some people call it PLOP).

Some time back I sent you a file that Plop would open that would give you
the specifications for your flotation mirror cell. If you want, I'll send it
again.

>I'm half way there since I have some sheet metal that is 1/8" thick, and
some hammered up sheet metal that is 1/4" thick.  (the latter is good for
small pieces, for larger pieces you would have to either run it through a
roller to make it smooth again or buy stock).

The 1/8" stock is thick enough.  Aluminum I hope. Steel will work but it is
heavier.

> 20InchFrameWork.jpg  to find a picture that shows the way I stiffened my
20" sonotube.

I guess as long as it isn't in front of the mirror, it wont interfer.  I'm
surprised that sonotube was that flexible.  My 12" tube for my 10" mirror)
is very solid.


>Then I started to think that the idea of the Couder mask is a good idea.
You could test different zones at different times, so I tried to make a mask
out of construction paper.

Okay, this is important.  You MUST make a Couder mask if you are going to
test your mirror.  While you are on the Stellafane web site getting the
plans for a mirror stand, go to the Couder mask design area.  You can get
the specifications for a proper Couder mask from the.  This isn't guesswork,
it must be done correctly.  Many people use a separate mask for each zone.
I recommend this approach.


>Also my friend Jerry says that I should use a pin hole test instead of the
knife test.  The University Optics Mirro-Test foucoalt tester is setup to
use two knife edges (one from each side).  So I modified it to use a pin
hole that I pierced in a piece of aluminum foil.

Okay

clear skies,
Jerry


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