Veneer & Foam Mat Dew/light Shield

[PeterStudz]

I don’t suffer from dew that often but in the few occasions that I have it’s obviously annoying. And there’s quite a bit of stray light when I view from my back garden in Southampton. 

At the end of last year I got a thin 4mm yoga mat (£6.50 from eBay) in order to make the standard foam mat plus Velcro strip dew shield for my small Skywatcher Skyhawk 1145P. Incidentally, good old fashion Evo-Stik contact adhesive (I prefer the stuff in a tin - see picture) bonds Velcro strip to foam mat so well that if you try and remove it, like I did in a test sample, you’ll take part of the foam mat away - ie the bond is stronger than the foam itself - it’s not going anywhere. 

Then, sometime back at the end of Feb this yr, I wanted to make a shield for my 8” Dob. The thin 4mm foam mat was ideal for my 4.5” telescope but far too floppy for an 8”. Not wanting to waste the foam that I had I went down the shed to see if there was something I could use to stiffen it up a little. There I found some thin veneer (0.45mm) from my model aircraft days. Using the trusty Evo-Stik I simply bonded the veneer to the foam, trimmed it all to size, wrapped it around the OTA and stuck it all together with more Evo-Stik. I also bonded a strip of veneer at the end just to prevent any splitting. Then finished of with tung oil in order to waterproof. Tung oil is also flexible. 

Simple stuff. The result is light (about 185g) and stiff. It all slips on with a tight fit. I also made a little version for the finder using veneer and 2mm craft foam. Of course it won’t roll down but I can live with that. 

[westmarch]

 

I like your setup Peter and I have similar dew shields on my main tube and RACI.  Despite this my RACI is always the first to dew up. Last week, I managed two hours before this happened. I put the scope into vertical position and placed an electric hand warmer, costing less than a tenner, on the objective end of the RACI. The dew cleared within five minutes and allowed me another hour at the scope.

John

[PeterStudz]

Thanks @westmarch. I think you are the person who started the thread  “10” Equatorial Platform for Dummies”. I’ve been following that with interest as it’s something I’d like to make. In fact it’ll probably be the next thing.

Thanks for the hand warmer tip. I’ll certainly try that. My red dot followed shortly by my RACI are there first to dew. Not that bothered by the red dot but when the RACI goes it makes life much harder. 

[Swoop1]

The most elegant looking dew shield I have seen for a while👍

[Mark2022]

Peter, is it still possible to find that veneer?

[PeterStudz]

13 hours ago, Mark2022 said:

Peter, is it still possible to find that veneer?

Hi Mark,

I’m not 100% sure but the veneer I used is almost certainly something called “obeche veneer”. Looking on the internet it seems to have gone out of fashion. In the good old days you could pop down to your local model shop and select a nice piece without splits and with a nice grain. It was cheap too and was also used for furniture and picture frames. It might still be possible to buy some somewhere.

Other thin veneers will probably work too. You need something around 0.5mm thick. From memory the veneer I used was 0.45mm.  Looking around The Balsa Cabin have poplar veneer which they say can be used for model aircraft wings, so it must be similar. Although I have no experience of using it, but it doesn’t cost much.

https://www.balsacabin.co.uk/product/poplar-veneer/

There are other thin veneers around including fleece backed, which is very flexible and should also work. But seems to be more expensive. You could try a small sample size of veneer first and make a finder size one. If it works on that it’ll be fine on something larger.

I first cut out the foam mat to size. Then bonded the veneer to the foam FLAT. This made it easy to form the cylinder of the dew shield. Although for the much smaller finder dew shield I soaked the veneer with water after It was glued to the foam using a brush before forming the cylinder. This did make the whole process easier.

I’ve been using these dew shields regularly for almost a year now and there’s been no splitting of the veneer, or any other issues. Hope that helps. If i see or find anything else I’ll let you know.

 

[Mark2022]

Thanks Peter.