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Philip R

Using thin rubber sheet for making a dew shield

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Hi all,

Does anyone know whether using thin (upto 2mm) rubber sheet (and self-adhesive velcro) is a suitable material for making a dew shield for a Mak or SCT? :iamwithstupid:

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Hi Phillip

Why not, as long as it creates its own air space it will work fine, I have made one out of foam matting bought from a camping shop and it works great. I have also buiit in my own home made dew heater on the inside of the shield which makes it even better.

Dave

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I wouldn't go with velcro (the brand), but I would use a hook and loop alternative, that is not as heavy duty. I would also not use the stick on type, as it simply does not work in damp cold conditions, in my experience it just peels off. Best to get some stitch on type and purchase a carpet / contact spray adhesive.

As for material, well my SCT has an old hard plastic celestron dew shield, that I bought with the scope. It works OK, but perhaps something a bit more moisture absorbent might make for a better alternative. That isn't to say that rubber is perhaps not a suitable material to consider (unless it is too heavy). If you flock the inside then you will also have an absorbent interior to. I made a dew shield for my dobsonian using light weight 9mm dark grey camping mat foam, which I also partially flocked and this seemed to work fine.  

Alternatively for an SCT, if you have the money, then there are some good commercial options.

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I hope it is OK as I have 3 sheets from Hobby Craft to make a dew shield out of, just have to make up my mind which colour to use black or blue.

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I wouldn't use thin rubber - it's too floppy for anything but very smaller apertures - you need a stiffer but malleable material like foam camping mats which can be picked up quite cheaply from a camping store (under a fiver). Black is the most popular colour as it absorbs all reflections. Choose matt black as opposed to gloss for the same reason. :)

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Hi Philip,

I use a foam exercise mat. I hold it in shape by two bull clamps and just slide it over my cpc 925 when it set up. Its blue in colour. So far the front lens has not fogged up, i forgot it once when i was up in the Dublin mountains and the lens all dewy. So it cheap but it works, it was bought in the pound shop. Hope my sister doesn't go looking for her mat ha ha.

Pauline.

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You may find that 2mm is a bit on the thin side and being rubber could have a tendency to attract moisture. Try it by all means, but if it fails then go for Black camping mat material, as other contributors have suggested, it being the most popular method :)  

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You didn't say what size scope you are wanting the dew shield for. I had a 6" SCT and used some black craft foam and velcro from a big box store, at a length of twice the diameter it worked very well. However I tried the same approach for an 8" SCT and at a length of twice the diameter it was just a bit too floppy and would collapse so I had to make one of stiffer but still light weight material. I used 3/16 inch plywood.

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Thanks for the advice. Might get one of those "off the peg" ones from FLO. Less hassle.

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For a small scope, 2mm craft foam sheet and double-sided tape works fine.  I also made a "hat" for my Rigel and a mini dew shield for my finder from this stuff.

For a bigger scope camping mat works well.  I hold mine together with long cable ties as the camping mat foam seems resistant to most glues.

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