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Post Info TOPIC: Dew Shield
Blobrana


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Dew Shield Heater
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Homemade Heater Strips

Search the Internet and you will find many different arrangements for building dew heaters. While they do work, most of them wire the resistors in series and if you need a different size heater then all the values change. You must also be careful not to exceed the resistor wattage or it could overheat and possibly even cause a fire. To avoid such problems, the instructions below will use 330-Ohm 1/2 Watt resistors wired in parallel. No calculations are needed with this method, simply space the resistors 5/8 inch apart. These heaters are compatible with the DewBuster Controller and other controllers that accept Kendrick heaters. There is no risk of exceeding the wattage rating and each resister will generate its full rated 1/2 Watt of heat when the controller is set to full power which means you will use the fewest possible resistors for the heater.
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Ed ~ Newtonian tubes effectively act like very long dew shields, so the mirrors rarely dew up.  So, an even cheap and easier way is just to extend a refractor or schmidt cassegrain dewshield with a stiff roll of card and/or plastic foam. A slight cone shaped dewshield will stop Vignetting of the telescope image.



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Blobrana


L

Posts: 131433
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RE: Dew Shield
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Home Made Adjustable Dew Heater

After putting up with ending several great observing sessions early because of the inevitable dew problems, I decided some active dew suppression was in order. I researched several different home-brew and commercial solutions and decided to build my own.
The Kendrick and Orion systems looked attractive, but expensive. Most of the home-brew systems involved gluing the resistive elements to the corrector of the scope, a route I did not want to take.! decided to design a system that would give me the best of both worlds: a neat, finished-looking end-product similar to the commercial ones, yet inexpensive to build and easy to use. My goal was to produce a unit that would not have a tacky homemade look but would complement the appearance of my scope (we all know how important that is).
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Blobrana


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Posts: 131433
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A Dew Shield is a hollow plastic, plastic/foam, or aluminium cylinder that slides onto the front of your scope. It has the advantage of blocking stray light (e.g. from your neighbour's porch light) and adding weight to the front of the scope which helps balance heavy items mounted on the scope's rear cell. Simple foam dew shields are offered by Orion as well as Meade.
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