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Old 06-07-2018, 08:02 AM
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Paul Haese
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Join Date: Jan 2009
Location: Adelaide
Posts: 9,937
That is quite interesting Dave, as I had gradients a lot with the GSO Newt too. I put that down to more light in the atmosphere from Adelaide and suburbs or because the there was not a front shroud. I never once considered this might be a problem because the fans were on and drawing air over the primary. That is supposed to keep dew from forming.

Perhaps the primary being a conical shape contributes with excessive cooling which pushed some parts of the primary below the dew point after a few hours with the fans operating. It might also only occur in areas of high dew too. What is your dew like each night? We have heavy dew generally each night at Clayton and moisture laden air would perhaps contribute.

I'm reluctant to put any heat into the primary as this can set up tube currents and movement of the primary if the heat is too high, not to mention how do you use a primary heater on a conical shaped mirror? Perhaps just turn the fans off after a few hours and see what happens. Have you tried that?
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