Re: [ATM] Is my mount right?

[buck childers <bchilders@everestkc.net>]

David,
I'm not going to be a whole lot of help but a couple points.

I doubt that support is going to keep the mirror from flexing.  With
those clamps it looks like it might even increase flexing.  A floating
point support is not that difficult to build even with common tools.  Do
a google search on the words: flotation mirror cell design (not the
phase just the string of words) or atm mirror cell.  You'll turn up
lots.

Plop is just a tool (software program) to help design and analyze mirror
supports.  For what you are doing now you can probably skip plop and go
with some fairly standard multi point support designs.  Net searches or
a trip to the library will find these.

>From the looks of the photos of your mirror it is not polished out yet.
Could be the photo or light source but it sure looks like you can see
the haze of unpolished glass.

While your friend in Stergis might use a Foucault test to determine if
its polished I wouldn't.  I would use an eyepiece and examine the
surface under a bright light.  Here's one article on the technique
http://www.atm-workshop.com/polish-test.html

Good luck,
-Buck

----- Original Message ----- 
From: "David Williams" <dwilliams1128@earthlink.net>
To: <atm@atmlist.net>
Sent: Thursday, August 12, 2004 4:07 PM
Subject: [ATM] Is my mount right?


Hello

I am making a 20" telescope and I posted pictures of the progress on it
at this site

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

and then you click on 20"Telescope Stuff and there are the pictures.

On some of the pictures you can see the plywood structure that I used as
a mount for the primary mirror.  I  have used a layer of 3/4" thick
weather stripping in a circle shape and then as a cross shape in the
middle.  I was wondering if this is orthodox procedure in the atm list.
Probably though I should use a floating point mirror cell or Plop, but I
don't know much or anything about either one of these things.

Either way I'm about ready to test out the mirror optically.  I have the
foucaolt tester and have done that already.  And a friend of mine Jerry
Martinsen from Stergis, MI who has made a few mirrors,  said that the
mirror is probably polished out now.  I told him that I can see my
reflection in the mirror directly over head and he said that isn't the
way to tell.  He said that the way to tell if it is polished is to do
the foucaolt test.  So I have the two mirrors the primary and the
secondary and the primary holder, I just need the spider and holder for
the secondary.  The man who's making that is Gary Wolanski.  He lives in
Vancouver BC.

Well thank you for your help.
David Williams
dwilliams1128@earthlink.net
Bye
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