If you find your scope isn't dewing up, then you are fortunate. But it will happen...
You certainly can make a dewshield out of whatever material that you have at hand. Foam is great because if you make it long enough you can also wrap the whole length of the OTA to insulate it, this way you eliminate any cooling wait period and are able to crank high magnification from it without the effects of a thermal plume because the insulation prevents this plume from forming. I've been insulating my SCT's and Maks for several years now and I've made these wraps double up in the purpose of insulation wrap and dewshield.
For the C5 I had I made out of Coreflute (1st pic). I've used Coreflute and a yoga foam mat (2nd pic) to make my wraps/dewsheilds. Many people use a material called Reflectix or any of the different similar types of material. It really just comes down to you as to what you prefer, with one consideration being it needs to be light weight so not to cause other problems with balance and excessive load. The dewshields I make easily come off for packing and the materials are all easy to cut so that they can be adapted to fit around items attached to the OTA such as finderscope shoes and dovetail plates.
Edited by maroubra_boy, 26 October 2021 - 03:37 PM.