[ATM] undercorrecting?

[J H M Gastel <jhm.vangastel@wanadoo.nl>]

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/
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