Length of a 9x50 finder scope dew shield?

[jonathan]

I intend to make one out of thin foam sheet (as available from The Works or similar stationary type shop), just wondering how long it should be. It should just slot over the end, perhaps be held in place by the dew heater tape or a piece of elastic.

[allcart]

In Theory it can be as long as you want to make it. As long as it does not obstruct the FOV or cause vignetting, or flap in a breeze it will be ok. My guess is about 2".

[Moonshane]

I did two layers of the 2mm foam and this created a quite solid dew shield. I then put an extra layer on the inside on the end that goes onto the finder. the shield is about 3" long of which an inch is on the end of the finder. with this and keeping the eye cap on, dew is kept at bay all night sometimes.

[ollypenrice]

I've hear it said that a dewsheild should be 1.5x aperture to be fully effective. I can't say that I've tested this claim, though.

Olly

[nightfisher]

I recently made a dew shield for my 9x50 finder, i used an empty 500ml "perfectly clear" drink bottle, i cut a 3 1/2" middle section of the plastic, and using fake carbon vinyl wrap fixed it around the end of then scope, and flocked the inside, little tip make it SLIGHTLY to big, then flock it and it will be a real nice push fit

http://stargazerslounge.com/topic/158918-9x50-finder-dew-shield-home-brew/