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Re: [ATM] undercorrecting?
I read part of his articles and read hat the difference in Strehl ratio for a slightly undercorrected mirror, warmed 2 degrees Celcius at the back side, goes from 0.66 to 0.99. The Strehl of another, cooled mirror, went from 0.51 to 0.79 after the same warming-up at the back side. He also says, that the radiation gives a 2 degrees C difference in temperature between front and back side of the mirror, so, according to Rohr, the effect is large. I don't know of any other research pointing in the same direction. Anyone else maybe? Or maybe evidence that it's not true?
> Datum: 03/08/06 11:55 AM
> Van: "laurence vincent"
> Aan: atm@atmlist.net
> CC:
> Onderwerp : Re: [ATM] undercorrecting?
>
> hello
> I already heard this assertion on behalf of proffessionel, to check it is
> more difficult.
> Look the work of Mr Wolfgang Rohr
> http://www.astro-foren.de/showthread.php?t=6454
> http://rohr.aiax.de/strehl-verb.htm
> Franck grière
> www.mirro-sphere.com
>
> ----- Original Message -----
> From: "J H M Gastel"
> To:
> Sent: Thursday, August 03, 2006 8:57 AM
> Subject: [ATM] undercorrecting?
>
>
> > Sometimes the topic of deliberately undercorrecting large mirrors comes
> up. On a Dutch mailinglist someone writes undercorrecting is necessary,
> because a mirror, even a mirror cooled with fans, will never reach
> equilibrium because of radiation of heat from the alumiumized surface of the
> mirror into the kosmos. Reason why the face of the mirror will always be
> cooler then the back side, which will deform the mirror. Maybe there is some
> radiation, but I can't imagine that, in the case of a well cooled mirror
> (well placed fans of sufficient capacity) the effect is so large that it is
> necessary to leave a large mirror undercorrected. Did I miss something?
> > Jan van Gastel
> > http://home.wanadoo.nl/jhm.vangastel/Astronomy/
> > _______________________________________________
> > ATM mailing list http://www.atmlist.net/
> >
>
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