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Dew shield made from camping mat.


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I picked up a camping mat yesterday to make a dew shield for my reflector. Now the thing i am not sure about is where to attach it to the scope because the scope is constructed from a tube that is half solid and the other half is open truss. Do i attach the shield so that the entire open truss part of the scope is covered or do i just attach it to the end of the scope where the secondary mirror is located and leave the open truss OPEN?

I am thinking i enclose the whole open truss area because i want to keep the primary mirror from fogging up.......as well as the secondary.

Thanks in advance.

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Ideally you should wrap something around the truss poles (as a light shroud) and have something extended above the secondary to stop stray light getting into the top of the tube as well. When I had a 12" truss dobsonian at light shroud was more or less essential to get any decent DSO observing done.

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*UPDATE*

Ok so today i bought a roll of self-adhesive Velcro (20mmx5M) of the stuff. It cost me just about 18 euro.

I now have a dew shield/shroud for my SW Heritage 130P, dew shields for BOTH objective lenses on my 20X90 bins and a dew shield for my Canon 450D.

All thanks to a camping mat and a roll of velcro.

Assembly time for ALL dew shields...........1 hour.

Cost=26 euro (approx)

The only reason i have done all this is because i live on the east coast of Ireland and i know from experience that the dew problem during the summer months here is atrocious. Without ANY dew prevention my lens's are fogged up and water running off of them within 20 mins.

Fingers crossed.............i am a bit more protected now.

Edited by LukeSkywatcher
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Can we see some pictures please???

Helen

I'll post soon as i can.

My dew shields/shroud are olive green. Should i worry about internal reflected light? They should be matt black.................

Would black shoe polish help?

Edited by LukeSkywatcher
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Ok so NO shoe polish. I'll find something else. Here's a couple of pics of the dew shields/shroud for Helen: I have left an inch of so on the primary mirror end of the scope shield just incase i need to enclose the secondary mirror/focuser. The shields for the bins i have cut down to size so that they are about twice in length that the diameter of the objectives are.

They may not be the prettiest things in the world but there is only so much you can do with a camping mat and a roll of velcro.LOL

My name is not McGyver.

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Edited by LukeSkywatcher
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:D re the mess... Nice job Paul. I've done much the same with a couple of bits of mine, I did have to cut down the dew shield for my 50mm as it was too long and impinged on the image, but it worked a treat.
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:D re the mess... Nice job Paul. I've done much the same with a couple of bits of mine, I did have to cut down the dew shield for my 50mm as it was too long and impinged on the image, but it worked a treat.

As is..........it does not hamper my view (no sagging) but i left a couple of inch to move it up towards the secondary and cut a notch in it to enclose the secondary if i find the secondary getting fogged up.

It actually took me about 20 mins to construct it and dew shields for my bins.

Edited by LukeSkywatcher
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  • 6 months later...
  • 2 months later...
I made mine with adhesive velcro but it doesn't stick very well to the campingmat foam. So perhaps duck tape is the way to go.

My first attempt failed in this way too, so my sister stitched the velco strip to the camping mat. No probs then. Until i gave it away. :)

When i needed another one, i didn't have the courage to ask my sister again and explain i had given away her last effort. So i bought the Velcro from Homebase which worked really well just as Luke describes. The self adhesive is very effective indeed.

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