How do you prevent a Mirador 20X spoting scope from fogging up?

[parrirc]

I have a Mirador 20X spotting scope that I use for high power shooting. I have had the scope for over 25 years. Every time the humidity gets high or a rain storm comes along my scope starts fogging up to the point I can't see through it. It fogs up on the inside. I understand some scopes are sealed with nitrogen to prevent fogging? If the seals go bad and the nitrogen leaks out then can fogging up start? What would be the most practical fix for the scope? We are not talking about a real high dollar scope here. Thanks to anyone who can give insight on this.

[joem]

Consider buying a new spoting scope as I don't know what the repair cost might be.

[dave]

Not hi value? Try drilling two or three holes around the scope body, like behind the front lense. Not huge holes, maybe 1/16 or smaller. May have to do same back in front of rear lenses. It has to 'breath', and keep it out of the rain. Don't drill into any internals!
Scope repair is really expensive!

[george r]

It fogs because it has trapped water vapor in it. Sounds like it was caught in the rain once. Over the long term that should lead to internal dust turning to visible fungus on one or more lens surface. Rather than wait, i would unscrew the eyepiece and place a silica gel packet inside and screw the eyepiece back on for a few hours to allow it to suck up the water vapor. Providing there is room inside that is (or providing that unscrewing one end lets you inside). Remove the packet on a dry day (or indoors if you have AC) and reassemble. You can repeat until you get the water out. Anyway test by putting it in the fridge to lower the temp of the internal atmosphere. When it doesn't condense at 40 or 50 degrees you are done. Even if it was once 100% nitrogen filled you are better off opening it up to let the water vapor out.

[parrirc]

I plan to pick up silica packs soon.

[Varmintpopper]

Check with your Drug Store, Small silica packets are often found in bulk pharmiceuticals and the pharmacist will probably give you a hand full for free.

Good Shooting

Lindy