I don't see why it would perform any differently than any other dew shield. If
you think about what the function of a dew shield is it shouldn't really matter
what it's made of as long as its opaque and durrable. What the dew shield does
is it cuts down on the amout of sky that the corrector plate "sees". (You may
already know all this, but I'll say it anyway.) This is called the view factor.
With a perfectly flat horizon, cloudless sky, and the telescope pointing
straight up, the view factor is very nearly 1. With a dew shield (I did this
calculation once, and am trying to recall the number off the top of my head) the
view factor drops down to about 0.17 + or - depending on the length of the
sheild. The amount of heat that the corrector plate radiates off into space is
4 4
Q = A*F*(Ta -3 )
(again off the top of my head). A is the area of the corrector plate, F is the
view factor, Ta is the temperature of the corrector plate (in Kelvin) and 3 is
the "temperature" of a black sky. So adding a dew sheild should reduce the
amount of heat radiating from the corrector plate into the sky by about 80%. A
small heater could replace the rest if your picky. So, any opaque material
should work well. I use a piece of laminated black construction paper that I
lined the inside of with felt. It curls into a tube and fastens with velcro
tape. Just made it this last weekend being boered with El Nino. Waiting for
the weater to get nice and warm so I can try it out.

Phil

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What is the best Dew Shield for the 12" LX200? (I just received a Plastic
flexible "wrap-around" dew / light shield from Kendrick's along with the
entire dew system for the 12" LX200) and was looking for comments on how
well this "plastic dew shield" performs compared with others?

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