Quote:
Originally Posted by fsr
I don't think that a fan can cool anything under ambient temperature, as the air is at ambient temp. It's the mirror itself that is cooling, by radiating it's heat to space.
Maybe more air is the solution to keep the mirror at ambient temperature?
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The direction of flow is the critical aspect with this problem. If the fans pull the air past the mirror then dewing is less likely to occur.
I have found that at my site which nearly every night has a humidity content of nearly 100% and very still conditions, that dew forms easily on everything. Most years I can gauge nearly 100mm of dew alone at a site that gets less rain that the Mt Lofty ranges.
These scopes have conical mirrors which cool very quickly and can come very close to ambient in these conditions. Some morning I have visited the site in winter and seen dew on the primary mirrors of the scope.