Yes, I did. From wikipedia (http://en.wikipedia.org/wiki/Vacuum): "In engineering, a vacuum is any region where the gas pressure is less than atmospheric pressure."
Yeah, parabolic dishes just don't seem to come naturally. (This particular one is made from mirrors with ?5? different circular curvatures arranged parabolically, if recall correctly) Some groups have made test dishes by applying a vacuum to the backside of a thin stainless steel sheet and heating it, then keeping it under a slight vacuum. This doesn't produce a perfect parabola, but it's better than circular, apparently. Some examples are here: http://www.psa.es/webeng/areas/instalaciones/disco s.html
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Yes, I did. From wikipedia (http://en.wikipedia.org/wiki/Vacuum): "In engineering, a vacuum is any region where the gas pressure is less than atmospheric pressure."
Yeah, parabolic dishes just don't seem to come naturally. (This particular one is made from mirrors with ?5? different circular curvatures arranged parabolically, if recall correctly) Some groups have made test dishes by applying a vacuum to the backside of a thin stainless steel sheet and heating it, then keeping it under a slight vacuum. This doesn't produce a perfect parabola, but it's better than circular, apparently. Some examples are here: http://www.psa.es/webeng/areas/instalaciones/disco s.html