Foggy optics in humidity?

[Sebastian the Ibis]

I have always had a hard time trusting anything other than iron sights. However, I am thinking hard about a red dot (likely an Aimpoint 512) for night time use on an AR in lieu of a tritium dot on the front sight post. ~ The past week without electricity has made me re-think some things.

One of my bigger concerns is any glass lens fogging up when taken from a cold air conditioned environment (i.e. Car or house) to a humid one (out doors in Florida). Has anyone encountered this, or done enough experimenting to know it's not an issue?

 

[Walkalong]

Cheap optics can fog up on the inside, quality one rarely do.

Any surface can form condensation on the outside surface when they go from hot to cold or vise versa, but it soon acclimates as it warms/cools to match the surroundings.

When I bring handguns to the range on a hot day they often flash over with moisture when I pull them out. I just let them sit a minute or two and it's gone.

 

[cdb1]

Never had a scope fog up.

 

[Skylerbone]

Personal experience bears out the truth of what Walkalong wrote. On early morning hunts when uncasing rifles and checking available light through scopes they all "fog" over for a short while. Mine range from $20-$800 and when it comes to external lenses it makes no difference.

In light of your unique circumstances and potential needs, it's not likely that it will be an issue excepting car carry since looters don't show as soon as the power goes out (meaning house temp will already have reached outside temp or near enough).

 

[bearcreek]

Could get 45 degree backup irons rather than cowitness. Irons would still be usable then even if the optic lense was occluded.

 

[jmr40]

I've NEVER had a decent scope fail me. I've had iron sights fail several times.

External fogging is user error. In cold weather you don't breath on the lenses and you don't take one from a hot room directly into cold. Never had a problem going from cold to hot. They need 1-2 minutes for temps to get right. Scope caps prevent water drops from getting on the glass.

Internal fogging means a defective scope. Buy something in the $200+ range and you'll never have an issue.

The benefits FAR outweigh the negatives. Keep magnification to 1X or no more than 2X and scopes are faster than irons. Any scope is much better in low light. Dot sights are a solution looking for a problem. They aren't any faster than low powered scopes, are harder to use, and are a poor choice in low light. While the dot is easy to see, the target is not. They make low conventional scopes with illuminated crosshairs. I'm not crazy about them, but are OK. If the battery fails you still have conventional crosshairs.

For night time use a high lumen small light attached to my AR handguard lights up over 100 yards away and I can see through a conventional scope (or irons) just fine.

 

[swampcrawler]

I live in Louisiana, so I understand exactly the humidity situation. Everything I have will instantly fog when going from nice cold dry AC to the sauna.

I have no idea how to stop it.

Rain will also make an exposed lense pretty much useless in my experience.

 

[MattB]

It does not matter how high quality of a scope you have when it comes to condensation on the outside of the lenses. If the dew point is high enough, it might not ever acclimate to the outside air (especially if you are in the shade). However, no quality scope should ever form condensation on the inside of the lenses. You will most likely have to keep wiping your scope lenses with a cloth to be able to see through them. The condensation can happen with any optic.

 

[bearcreek]

Anybody ever used some of that anti fog spray stuff that's made for glasses or shower mirrors?

 

[illinoisburt]

Anybody ever used some of that anti fog spray stuff that's made for glasses or shower mirrors?

I would not do it. The lenses have multiple chemical coatings to help transfer light and reduce glare. The spray might damage those coatings. Best to ask the manufacturer first!