University Lowbrow Astronomers

Effective and Very Inexpensive Dew Shield Material!

by Harry L Juday
Printed in Reflections: October, 2001.

We have been lucky this summer with rather dry viewing nights, on the ones we’ve had that is.  However, late summer and fall can bring out the dew, and fog up the seeing pretty fast.  Although I have a number of the great Kendrick dew zappers for my 8” SCT, eyepieces and even the eyepieces on our 10x70 binos, I needed something for my 18” Dobs.  I found what I think is a very good material, that I find works very well in absorbing moisture, can be pieced together for large applications (OK, it may not be the prettiest looking when it’s pieced), but it WORKS, and it is VERY INEXPENSIVE !!!  It is called “Flex-Foam”, made by “Fiber Craft Materials Corp” of Niles, IL.  It comes in approx.  12’ x 18” x 1/16” sheets, can be easily cut to shape, glued, stapled, wrapped around the end of a scope or spotting scope, velcro’d, rubberbanded, or whatever suits your fancy.  Also, it is available in BLACK !  It is a spongy mat’l so it is non-reflective, and is non-toxic, should anyone decide to bite it.  I found it at “Michael’s” in the children’s craft area.  It is (or was), less than $1.00/sht.  It seems ideal for smaller applications.  I use it on my spotter scopes and the objective end of the binos and have never had them dew up.  And it can get pretty damp at my place during the right weather conditions (I occasionally get fogged out).  I did piece together a long strip to use as a dew shield for the end of the 18”, however that does have a slight drawback.  Although it really picks up the moisture, and seems to do a great job preventing dewing, it sagged a bit when it got real damp.  To cure that, I purchased thin plastic strips, (24” x 1 1/4” x 1/64) at Ryders, glued two of them together (following the curve of the shield) sprayed them black (Krylon Ultra Flat Black - great paint for astronomy item use), and I velcro them to the inside of the dew shield.  It has solved the sag problem.  So, if you are looking for an easy to make, inexpensive material for dew shields, you may want to give it a try.


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