Re: [ATM] new type of floating cell

["jamoore47" <JohnMoore47@mail2web.net>]

oops!,,,,
I spoke too-soon,,,,
I found Mr.Gastel's post,,
Please forgive,,,
coffee hasnt kicked-in,,,,,
 
John Moore.
atm since 1974.

________________________________

From: atm-bounces@atmlist.net on behalf of Tom Krajci
Sent: Wed 10/18/2006 11:25 PM
To: atm@atmlist.net
Subject: Re: [ATM] new type of floating cell



>From: "Jan van Gastel" <jhm.vangastel@wanadoo.nl>

>First, the elasticity ratio of the mirror and the mat should be high (mat
>much softer then mirror)....

Does the article address how well this cell design will maintain tilt
collimation?  (Off the cuff it seems the mirror will tilt a good bit in the
cell as the OTA elevation changes.)

Does the article address how well this cell design will restrict lateral
shift of the mirror?  (Off the cuff it seems the mirror will shift laterally
as OTA elevation changes, because I assume this 'very soft mat' will have
very low resistance to shear forces...and the mirror will shift downward as
the OTA is pointed near the horizon.  That's another way to spoil
collimation.)

Off the cuff it seems that a mirror, resting on such a soft pad...will
'piston' longitudinally as OTA elevation changes.  Does the article mention
how its lateral support scheme will handle such pistoning of the mirror
without interfering with the other functions of the cell?

>Cooling will take (much) longer as compared to a PLOP cell, because the
>mirror can only be actively cooled at the aluminiumized side.

I won't call this a show-stopper, but I consider it a significant design
disadvantage.

>Like I already wrote, I don't understand a lot of the math involved. But
>assuming the math is right, it will work theoretically....

I'm not yet convinced that it will work theoretically (even if the math is
right).  Did the article mention any real-world cells successfully built on
this principle?

Over time I favor more and more a stiffer approach to mirror cells...such as
a scheme with three hard-points that contact the mirror and define the
collimation plane...and multiple astatic levers to provide the 'flotation'
(axial force) support.  Lateral support is a different matter entirely, but
I don't want to go there tonight.

-------------------------------------------
Tom Krajci
Cloudcroft, New Mexico
http://overton2.tamu.edu/aset/krajci/

Center for Backyard Astrophysics (CBA)
http://cba.phys.columbia.edu <http://cba.phys.columbia.edu/>  CBA New Mexico

American Association of Variable Star
Observers (AAVSO): KTC http://www.aavso.org/
-------------------------------------------



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