DIY Dew Shield

[bosun21]

I recently bought a 12” dobsonian and a 12” astro essentials dew shield. To my surprise the dew shield is several inches too short to encircle the tube. The only other one I can see is the Meade 14”-16” SCT dew shield at £115. I’m going to have a go at making my own but don’t know what the best materials would be. Any recommendations would be appreciated. Thanks  

        Ian 

[geeklee]

10 minutes ago, bosun21 said:

Any recommendations would be appreciated.

Hi Ian - I picked up some cheap, thin camping mat and that seemed to work well.  Measured up with an overlap, cut, glue, done.  I also flocked the inside - this made a big difference visually as the camping mat - while black - was still a little "shiny".  The flocking didn't stick as well as I'd hoped but that's what a revision 2 is for!   This was used for an imaging scope.  Hope this helps.

Edited January 18 by geeklee

[bosun21]

I bought a camping mat previously but I tried Velcro etc and it wouldn’t stay closed. What glue did you use?

[geeklee]

1 minute ago, bosun21 said:

What glue did you use?

Gorilla glue - I think it may have been slightly expanding stuff where its moisture activated.  Maybe not be the most appropriate but the strongest I could find in the garage at the time! Once glued, I taped it up around the join until it had set/cured.  This was just mat-to-mat, no velcro.

[bosun21]

I will give it a go as £115 is a bit much for what you get.

[jjohnson3803]

I use craft foam sheets for dew shields and other things.  Roll into a cylinder and hold sides together with duck tape.  I imagine there's a UK equivalent available.

 

Foam sheets

Edited January 18 by jjohnson3803

[markse68]

You can buy polypropylene sheet from craft shops which is similar, possibly the same stuff the commercial dew shields are made from I think. It’s cheap and easily cut with a stanley knife. I used the 50mm wide extra strong self adhesive velcro along the edge and it’s a b*****d to unfix but does the job well

Mark

[Gfamily]

7 hours ago, bosun21 said:

I recently bought a 12” dobsonian and a 12” astro essentials dew shield. To my surprise the dew shield is several inches too short to encircle the tube. The only other one I can see is the Meade 14”-16” SCT dew shield at £115. I’m going to have a go at making my own but don’t know what the best materials would be. Any recommendations would be appreciated. Thanks  

        Ian 

I got a sheet of proplex* from Wickes for about £5 for a 2.4 X 1.2 m sheet.

Cut to size and use sticky velcro pads to hold it closed.

* twin walled sheeting used by builders to protect flooring. 

Lightweight, flexible, folds flat when not in use.  Hard to think of anything easier.

 

[Dave scutt]

10 hours ago, bosun21 said:

I recently bought a 12” dobsonian and a 12” astro essentials dew shield. To my surprise the dew shield is several inches too short to encircle the tube. The only other one I can see is the Meade 14”-16” SCT dew shield at £115. I’m going to have a go at making my own but don’t know what the best materials would be. Any recommendations would be appreciated. Thanks  

        Ian 

I made a dew shield from a yoga matt but after a while it started to lose shape.

So I brought a 12"  lynx astro one and as the same as you they are too small.

I brought some velcro from amazon a few inches wide which connected it together,  covered that section with some flocking material I had left over , and now it works fine.

[bosun21]

I’ve already sent mine back. It was a good three inch gap so no use to me. The Meade 14-16” is £115 which I refuse to pay. I have just ordered a 1m x 2m sheet of closed cell polyethylene foam and a bottle of gorilla glue which holds it together really strongly. I hate messing around with Velcro as it’s got a habit of coming off.

Edited January 18 by bosun21
Typo

[Mike Q]

I made mine out of 5mm EVA foam, velcro and duct tape.  So far so good.  You can get it done for less then 20 pounds easy 

Edited January 18 by Mike Q

[bosun21]

I’ve just ordered everything I need but I’m going to use glue rather than Velcro. Holds together solid.

[Ratlet]

If you have issues with the foam, give me a shout.  I've got miles of underlay from a vinyl laminate floor I put down.  2mm thick, light as a feather and tough as boots.  I'll sling some in a tube and post it.

[bosun21]

1 hour ago, Ratlet said:

If you have issues with the foam, give me a shout.  I've got miles of underlay from a vinyl laminate floor I put down.  2mm thick, light as a feather and tough as boots.  I'll sling some in a tube and post it.

Thanks 👍 I’ll see how I get on with this polyethylene sheet I’ve already bought. I’ve had a bad time with foam in the past. The Velcro adhesive side just pulling away and bringing foam with it. It ended up in the bin. Thanks for your offer and I may yet call on you.

     Regards  

          Ian 

[apaulo]

i used a 3mm yoga mat of ebay, put a 2" self adhesive velcro strip on it and ran a sewing machine around the edge of the velcro. no problems so far after a year.

[bosun21]

11 minutes ago, apaulo said:

i used a 3mm yoga mat of ebay, put a 2" self adhesive velcro strip on it and ran a sewing machine around the edge of the velcro. no problems so far after a year.

Ah, ha the old sewing machine trick! That would definitely hold the Velcro in place. Problem is I don’t have one. Never have. Thanks for the information.

[PeterStudz]

On 19/01/2023 at 22:53, bosun21 said:

Ah, ha the old sewing machine trick! That would definitely hold the Velcro in place. Problem is I don’t have one. Never have. Thanks for the information.

Only just noticed this thread so you’ve probably made yours by now. But I found that good old Evo-Stik contact adhesive stuck foam mat together really well. I’ve made a couple of dew shields with it and the bond has held for over a year.

You can buy Evo-Stik in smaller size tubes too. 

Edited February 10 by PeterStudz

[bosun21]

1 minute ago, PeterStudz said:

Only just noticed this thread so you’ve probably made yours by now. But I found that hood old Evo-Stik contact adhesive stuck down Velcro to foam mat really well. Doing a test the only way to pull the Velcro off the mat would take part of the mat away too. In other words the bond was stronger than the mat.

You can buy Evo-Stik in smaller size tubes too. 

Thanks, but my impatience got the better of me and I ended up buying the Meade 14-16” dew shield for £115. Each time I made one they would sit badly wilting out of shape. I have made them for scopes up to 8” without issue, but the 14” diameter beat me.

[PeterStudz]

15 minutes ago, bosun21 said:

Thanks, but my impatience got the better of me and I ended up buying the Meade 14-16” dew shield for £115. Each time I made one they would sit badly wilting out of shape. I have made them for scopes up to 8” without issue, but the 14” diameter beat me.

Just out of interest… The one I made for my 8” Dob had thin veneer (for model aircraft foam wings) to stiffen it. Stuck to the foam mat which was just 4mm thick. It’s as stiff as a very stiff thing

[Merlin]

I glued my camping mat ends together with common or garden Uhu. Works fine, no tape needed.

[bosun21]

On 10/02/2023 at 10:06, PeterStudz said:

Just out of interest… The one I made for my 8” Dob had thin veneer (for model aircraft foam wings) to stiffen it. Stuck to the foam mat which was just 4mm thick. It’s as stiff as a very stiff thing

I have made several for 8” dobsonian but the tube on my 12” is 14” in diameter which caused my foam attempts to sag out of shape. I wish I had some of that veneer you had 🤔

[PeterStudz]

4 hours ago, bosun21 said:

I have made several for 8” dobsonian but the tube on my 12” is 14” in diameter which caused my foam attempts to sag out of shape. I wish I had some of that veneer you had 🤔

Although as is often the case it wasn’t as simple as it sounds. The foam I bought was fine on its for my little 4.5” reflector but would sag (it’s only 4mm after all) when I tried it out on my 8”. Not wanting to buy another bit of foam - what thickness would work? - I thought of doing other things, eg doubling up the foam, stiffing with card… in the end I found the veneer down my shed from my model aircraft days. 

In other words - I was a bit lucky. Dew shields are great and I couldn’t do without them now. 
 

PS - one thing that can be forgotten is that for a Dob it’s useful if your dew shield is not too heavy. The thin veneer that I used doesn’t weight much but getting a really thick piece of foam so that it doesn’t sag can be surprisingly heavy. 

Edited February 12 by PeterStudz