Finder Scope Frost Shield

[andyc277]

I am after some confirmation from the DIY gods. I was out making sure the stars hadn't fallen down in about -2degC. After about an hour my Finder scope front lens had frozen over, main scope was fine. Would a foam/plastic cover around the end solve the problem? If so what sort of length? Ive had a look at Dew Shields etc and I think what I have seen and read would solve the problem.

[jimmyjamjoejoe]

It would certainly slow it down. I think the general rule for dew shields is double the aperture in length, so for an average 50mm finder you want the dew shield to extend 100mm past the objective.

[pwalsh61]

When I first started using my 9x50 finder I found it would fog up so I made a shield by sandwiching sheets of black paper and bubble-wrap together. I found that an A5 sheet would wrap around the finder nicely with a bit of an overlap where I used a glue stick (Pritt-stick) to glue the ends of the paper together. Two wraps of paper followed by one of bubble-wrap followed by two of paper. Thin card would work better than paper as even with those layers it's a bit flimsy. Alternatively, neoprene foam would work. Either way, I haven't had a problem with dew since

[Gina]

Sounds good

[m.tweedy]

some left over camping mat and rubber bands works for me. (and the finderscope )

[Stargazer33]

Yep, a tube of foam camping mat material held together with duct tape keeps my finder scope dew free all night. I think mine is about 3 times longer than my finder scope objective diameter - 30mm.

[andyc277]

Thanks for the replies guys. Foam will be sourced imminently