Primary Fans and Dew

[BlueAstra (Graham)]

I have a RC scope with primary fans. They draw air from open front of the scope, over the mirror and out through the back. Do these fans in any way delay dewing, or are they just for cooling the mirror down to ambient? If I put a dew strap around the tube near the mirror, And the fans are running, won't the constant flow of cool air negate its effect? So in a 'dewy' environment should I turn the fans off and just rely on the dew strap? The scope is in an observatory so is generally at ambient temperature.

Graham

[Joshua Bunn (Joshua)]

Graham,

I don't know if they delay dewing, but the other important function of the fans is to keep a steady flow of air over the mirror and through the tube to prevent tube currents. I would run both, see how it goes. I have primary and secondary temperature control on my scope and leave the fans running all the time. never had dew problems in a dewy environment, but the mirrors are kept just above ambient.

Josh

[BlueAstra (Graham)]

The scope is in a roll of roof shed, so not fully enclosed. I did experience dewing on the primary and secondary during one particularly cold and damp night. I've installed a secondary heater but I've nothing currently for the primary. I was thinking of using a dew strap around the case and turning the fans off.