Re: [ATM] Ball bearing for triangles

["A. Suijkerbuijk" <a.suykerbuyk@wxs.nl>]

Bonjour Rafaël,

Your information is very interesting. "Classical theory" (books, articles
etc.) says that the back side cools faster since there is no aluminum on it.
Perhaps in the case you mentioned (very thin mirror) things are different.
Perhaps the mirror will reach the air temperature very fast, after which the
aluminum side radiates most. In this case the mirror will cool below the air
temperature? Or perhaps the meniscus plays a certain role.
About you mirror: You wrote that you see some spherical aberration in the
star test. is it overcorrection or undercorrection? I suppose this is after
cooling? Thanks!

Regards,
Adrie Suijkerbuijk


----- Original Message ----- 
From: "Raphaël GUINAMARD" <rguinamard@infonie.fr>
To: <atm@atmlist.net>
Sent: Sunday, September 05, 2004 5:27 PM
Subject: Fw: [ATM] Ball bearing for triangles


>
> ----- Original Message ----- 
> From: "Raphaël GUINAMARD" <rguinamard@infonie.fr>
> To: "A. Suijkerbuijk" <a.suykerbuyk@wxs.nl>
> Sent: Sunday, September 05, 2004 4:44 PM
> Subject: Re: [ATM] Ball bearing for triangles
>
>
> > Hi Adrie
> > No the mirror has a classical one face aluminated.
> > The aluminated face has a lower temp because it sees the space which has
a
> > 3K temperature.
> > The other face sees the ground and its 270-300K temperature.
> > The gradient of temperature of the 2 faces cause spherical aberation. In
> the
> > example of the 1.5 m mirror with a 28 mm  thick mirror (meniscus) the
> > difference of temp is about 0.8° and cause a very big (10 wave !)
> spherical
> > aberation
> > So what they've done is to heat the aluminated face whith a courant to
> heat
> > the upper face and suppress the sperical abberation.
> > To heat in a very constant way, they've put 40 groups of electrodes.
> > What could also be done (maybe more easy) is to heat the upper face with
a
> > infrared laser...
> > ----- Original Message ----- 
> > From: "A. Suijkerbuijk" <a.suykerbuyk@wxs.nl>
> > To: "Raphaël GUINAMARD" <rguinamard@infonie.fr>; "ATM Group"
> > <ATM@atmlist.net>
> > Sent: Thursday, September 02, 2004 8:16 PM
> > Subject: Re: [ATM] Ball bearing for triangles
> >


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