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The Kendrick Dew Prevention/Removal Systems, January 1996
When the temperature of a lens, mirror or mechanical component drops below the ambient dew point, then what ever moisture is
in the air will begin to condense on the surfaces. Moisture build up from dew on a good telescope does not generally cause any
long term damage unless the telescopes is packed away in a case while wet, or if it is stored in a damp location for a long
period of time; these practices can result in the build up of damaging Fungus. But the build up of dew on a telescope in the
field occurs over a matter of minutes or hours. If it does develop then it can manifest itself to an observer as a gradual
loss of contrast, with a view of brighter objects that appears as if one is observing through a cloud; this is especially
frustrating if one is dewed out during the course of a long exposure astrophotography session.
We at Company Seven had known many heating methods and systems sold by other companies and while some of these essentially do
work they were not as refined as we would have liked to see. The older systems on the market were unregulated and varied from
lens shields, to heating strips or lens shields incorporating resistive elements. Some people employed 12 volt DC powered hair
dryers to dry the optics of the telescope but, unless done carefully the telescope optics were likely to be temporarily
distorted by excessive heating to the point of producing less than nominal images until the lens or mirror cooled down.
In 1994, we were advised by Roland and Marge Christen of the Astro-Physics Company that they had met with a person that was making heaters that actually worked, even with the most sophisticated apochromatic refractors they made, even when using the telescopes at high magnification. Even then we remained a bit skeptical until we received samples of the Kendrick components for evaluation. Since then the proof is in the fact that where ever you see our telescopes in operation, you will see Kendrick dew remover/prevention components attached!
The Kendrick Dew Remover System is a modular system composed of a electrical resistive heating element, and a control box. When the correct size of element is placed around a lens or other component, and if the controller is properly set, then the heater can keep the temperature of the protected object just above the dew point. The result typically do not have a detrimental impact on the optical imaging qualities of the system - regardless even if there were, the alternative of dew build up is less desirable. For a complete review of the system components, and how they function then read the instruction manual that was written by Company Seven and provided by us with each controller that is sold by us.
The Kendrick Dew Shield is essentially a lens flexible plastic shield that can be stored flat, or around a telescope
tube for ease of transport. In operation, the shade is positioned around the objective of a telescope and then is fastened in
place with its Velcro material. The shields are designed to accept the optional dew remover heating elements. Some shields
(such as the model for the Celestron 11 inch Schmidt-Cassegrain telescope) will have cutaway sections to accommodate
counterweight bar assemblies or mounting hardware.
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