Telrad dewing

[Spile]

I wonder if these will work?

 

[Neil H]

It may work tried rainx on a visor  didn't work due to glass having tiny pits and the rainx fills them it and make the glass smooth so the rain can't stick and visor does not , but this says for glass and visor 

I have a cover on mine I just pull it off use the telrad then refit it so it does not dew up I think wookie1965 made a heater for his 

Edited February 7, 2021 by Neil H
Kindle puts in its own words

[Zermelo]

The anti-fog is an interesting idea I hadn't thought about.  I have some for the bathroom mirrors, I might give it a try.

Some other DIY efforts:

http://www.homebuiltastronomy.com/downbino/HomeBuiltAstronomy-TelradDewShield.html

http://www.astromadness.co.uk/p/diy-telrad-dew-heater.html

 

[Spile]

I've used RainX for years on the rear window of my wiper-less car. I find it great for water hitting the windscreen in that it clears but it doesn't work as well for me when it comes to water settling AKA dew.

[Phil]

I had some nichrome wire and heat shrink left over from making dew heaters for my OTAs so I made a dew heater for my TelRads. I tightly wound the heat shrink wrapped nichrome around a length of ductile garden wire. I had shrunk the heat shrink onto the nichrome wire beforehand. Electrically the nichrome wire and the garden wire run in series. I then put larger diameter heat shrink over whole lot. It was then just a matter of forming the heater into the shape you see in the picture to fit into the Telrad and applying a touch of epoxy resin glue to keep it in shape. The heater is held in place by friction so that it can be removed. 

[Spile]

The low tech option is working for me.