Can you prevent scope fog?

[Doobie]

Was out in the torrential down pour yesterday with my Ruger American 243 topped with a Vortex Diamondback 4-12x40 with Butler Creek flip up scope covers. As I crested a ridge(after walking almost a mile), a spike jumped up, ran about 20 yards and stopped...facing me. I shouldered my rifle, flipped the scope covers open, and all I saw was fog The outside of the rear lense was fogged up...I tried to quickly wipe it away, but being it was pouring down rain and my gloves were wet, no dice. Needless to say, the lil beast got away I pulled the bottom of my dry sweat shirt out, wiped the lense, and closed the cover. When I opened it again, fog(rear only). To say that I was pissed is an understatement. The only buck I've seen in Maryland during the past 4 hunting seasons, and this happens
I had purposely left my rifle in my truck all week in hopes of preventing this sort of thing, thinking that it would help if I didn't take it in and out of the house(change in temps). While driving to where I was hunting, I didn't use the heater and kept my window open somewhat. I have the same scope covers on an 18 year old Swift scope on another rifle, and that has never happened to me while hunting in similar conditions. What can I do to "treat" the lenses to help stop that? I've read that you have to watch what you use being that certain chemicals can harm the coating on the lenses. Had it been a trophy sized buck or 20 years ago, Vortex probably would have been receiving a scope back in the shape of a "U" complete with tree bark attached lol.

 

[magnumpi]

I have used this on my scopes and eyeglasses, works pretty good

https://www.amazon.com/Zeiss-Anti-D...id=1481159489&sr=8-13&keywords=anti+fog+spray

 

[Doobie]

I have used this on my scopes and eyeglasses, works pretty good

https://www.amazon.com/Zeiss-Anti-D...id=1481159489&sr=8-13&keywords=anti+fog+spray

Awesome...thank you
I will give it a try

 

[Half-cocked]

1. Keep your breath away from your optics. Blow/breathe away from your eyepiece, especially.
2. Keep your scope WARM. Moisture condenses on cold surfaces. Don't use your breath, obviously. Keep it in the sun, if possible.
3. Install and use scope covers, and open them only when a shot presents itself.
4. Keep your optics meticulously clean. This helps delay the onset of condensation. Use qtips and methanol (yellow HEET gas line antifreeze) to clean your optics.
5. If you ever see condensation on the inside surfaces of your optics, it means water/moisture has gotten in there. In that case, your only real option is to send it to the manufacturer for repair.

 

[Doobie]

1. Keep your breath away from your optics. Blow/breathe away from your eyepiece, especially.
2. Keep your scope WARM. Moisture condenses on cold surfaces. Don't use your breath, obviously. Keep it in the sun, if possible.
3. Install and use scope covers, and open them only when a shot presents itself.
4. Keep your optics meticulously clean. This helps delay the onset of condensation. Use qtips and methanol (yellow HEET gas line antifreeze) to clean your optics.
5. If you ever see condensation on the inside surfaces of your optics, it means water/moisture has gotten in there. In that case, your only real option is to send it to the manufacturer for repair.

Thanks for the suggestions/help

1: I'll try, but sometimes its almost impossible while "cheeking" the rifle with the wind/rain blowing.
2: How do I keep my scope warm while out in the woods hunting(a neoprene cover maybe)?
3: I already have Butler Creek flip open scope covers installed and didn't open them until I was ready to shoot at the deer.
4: I didn't meticulously clean the scope...I took it out of the package, installed Butler Creek scope covers, sighted it in, closed covers until I opened them to shoot at the deer. They appeared clean...guess I should've cleaned them anyways. Yellow HEET won't damage the lens coatings or surrounding seals?
5: At first I thought the fog was on the inside...luckily it wasn't. I woulda been pissed x2 if that were the case being its a brand new scope(although I know that doesn't always mean anything lol).

 

[Tracker]

Or you can try the scuba method of spit in your mask and rub it around. Then a quick water rinse. Sorry, probably not very helpful

 

[DaemonAssassin]

I have found that using scope covers like that will trap moisture and allow it to condense at the worst possible time. I will not use scope covers on optics, during hunting season for that very reason.

 

[Doobie]

I have found that using scope covers like that will trap moisture and allow it to condense at the worst possible time. I will not use scope covers on optics, during hunting season for that very reason.

I always assumed the opposite (ya know all about assume) and have used them for years without a problem. First time for everything I guess. I woulda been screwed without them too I imagine seeing as how hard it was raining lol.

 

[Indiana Jones]

Fogging on the outside is not fun, but it happens. The inside is when you worry. Outside try anti fog wipes.

 

[outrider58]

Two main points. First one was covered, don't breathe on it. Second, I always try to acclimate my gun to cold weather by putting in my truck the night before. This is not always practical for a lot of folks, though.

 

[Flametamer]

Scope covers will trap inside (between the cover and the lens) whatever is present when they are closed. They will also delay the transmission of heat energy from outside to the lens, and vice-versa, by virtue of the trapped air pocket, which can act an an insulator. Pretty simple physics at play here. Small leaks in the cover-scope seal will impact the speed with which energy and/or moisture travel through the cover barrier. So what does this mean?

I used to store the rifle in the truck overnight before a morning hunt. Ambient temperature declines after the sun sets, and the temperature continues to decline until after the sun is ~ 10-15 degrees above the horizon on a sunny day. (This assertion ignores/negates the not always trivial effects of a cold front or a warm front moving into the area.) So I have a scope at temperature X and, depending on the time I take the shot, air at temperature X+2; the covers are flipped open, and warmer air rushes in, meets the cold lens, and voila, condensation on the lens :-(

After I thought about the physics, I have not had the problem recurr. I do what I can to ensure that the lenses are at the same temperature and humidity as the ambient air. Leave the covers open or slightly adjar as much as I can.

I have also used a quiet piece of fabric to cover the scope and action on rainy days, or when there is a lot of dew on vegetation I am moving through. Not waterproof, since these tend to make more noise that I want to make when being removed, but something to deflect droplets and spray, and open enough to allow air to pass to the scope to maintain equilibrium. I also leave the covers behind much of the time since I rarely hunt in the rain or nasty dusty conditions these days.

I toyed a bit with a battery-powered heat 'blanket' or heater for the scope to keep it above ambient temps several years back. Think battery-powered socks here. It worked well, both in the lab and in the field. Just became too much trouble to carry around. I suppose it could be built into a scope, but I really don't see that many days where the expense or trouble would be really justified.

 

[Inigoes]

I have found that using scope covers like that will trap moisture and allow it to condense at the worst possible time. I will not use scope covers on optics, during hunting season for that very reason.

This

I always keep a scope cleaning cloth or hanky handy, just in case during wet weather.

 

[lx1x]

Rainx antifog .. a small microfibre cloth..

 

[lazarus]

Leave the scope covers OPEN until you need them closed. Especially if the scope is warmer than the environment it is in. If you are aclimating it in your vehicle ahead of time, leave them open so any temperature/humidity gradients can equalize.

Out hunting anywhere moisture could accumulate on it, leave the covers off unless you are in dense brush or precipitation. Of course that only matters if the temp and humidity are near the dew point.

Admittedly all of that experience is from photography, but I have a lot of years of experience keeping lenses and view finders fog free (and the rare instance of getting them fogged up)

 

[DutchV]

Try Cat Crap to keep lenses clear. REI carries it. I use it on my motorcycle lens and it seems to work.

 

[Pinecone]

Leave the scope covers OPEN until you need them closed. Especially if the scope is warmer than the environment it is in. If you are aclimating it in your vehicle ahead of time, leave them open so any temperature/humidity gradients can equalize.

It anything is WARMER than ambient, there is no issue with fogging.

At or below ambient is where there is a problem with fogging.

 

[lazarus]

It anything is WARMER than ambient, there is no issue with fogging.

At or below ambient is where there is a problem with fogging.

Yes, but if it is warmer than ambient, it means you'll trap warmer air, which can carry more moisture in it, between the lens cap and the lens element. As it cools down as you are aclimating the rifle/scope, that moisture will condense on everything.

This is why when you want the lens cover off while aclimating and THEN close it when it is done aclimating.

 

[Doobie]

Two main points. First one was covered, don't breathe on it. Second, I always try to acclimate my gun to cold weather by putting in my truck the night before. This is not always practical for a lot of folks, though.

My rifle was in the truck all week up until I went into the woods. Maybe warm air got trapped in between the covers when I closed them up in the house(as Flametamer mentioned) before storing in my truck.

Fogging on the outside is not fun, but it happens. The inside is when you worry. Outside try anti fog wipes.

Scope covers will trap inside (between the cover and the lens) whatever is present when they are closed. They will also delay the transmission of heat energy from outside to the lens, and vice-versa, by virtue of the trapped air pocket, which can act an an insulator. Pretty simple physics at play here. Small leaks in the cover-scope seal will impact the speed with which energy and/or moisture travel through the cover barrier. So what does this mean?

I used to store the rifle in the truck overnight before a morning hunt. Ambient temperature declines after the sun sets, and the temperature continues to decline until after the sun is ~ 10-15 degrees above the horizon on a sunny day. (This assertion ignores/negates the not always trivial effects of a cold front or a warm front moving into the area.) So I have a scope at temperature X and, depending on the time I take the shot, air at temperature X+2; the covers are flipped open, and warmer air rushes in, meets the cold lens, and voila, condensation on the lens :-(

After I thought about the physics, I have not had the problem recurr. I do what I can to ensure that the lenses are at the same temperature and humidity as the ambient air. Leave the covers open or slightly adjar as much as I can.

I have also used a quiet piece of fabric to cover the scope and action on rainy days, or when there is a lot of dew on vegetation I am moving through. Not waterproof, since these tend to make more noise that I want to make when being removed, but something to deflect droplets and spray, and open enough to allow air to pass to the scope to maintain equilibrium. I also leave the covers behind much of the time since I rarely hunt in the rain or nasty dusty conditions these days.

I toyed a bit with a battery-powered heat 'blanket' or heater for the scope to keep it above ambient temps several years back. Think battery-powered socks here. It worked well, both in the lab and in the field. Just became too much trouble to carry around. I suppose it could be built into a scope, but I really don't see that many days where the expense or trouble would be really justified.

I will definitely try leaving the covers open or ajar next time. And I was thinking of something along the lines of keeping the scope warm as you mentioned(and the heated socks came to mind lol)

This

I always keep a scope cleaning cloth or hanky handy, just in case during wet weather.

I do now

Rainx antifog .. a small microfibre cloth..

I'm going to try that

Leave the scope covers OPEN until you need them closed. Especially if the scope is warmer than the environment it is in. If you are aclimating it in your vehicle ahead of time, leave them open so any temperature/humidity gradients can equalize.

Out hunting anywhere moisture could accumulate on it, leave the covers off unless you are in dense brush or precipitation. Of course that only matters if the temp and humidity are near the dew point.

Admittedly all of that experience is from photography, but I have a lot of years of experience keeping lenses and view finders fog free (and the rare instance of getting them fogged up)

Try Cat Crap to keep lenses clear. REI carries it. I use it on my motorcycle lens and it seems to work.

I read about this...many people rave about it. At first I thought they were joking due to the name lol


This is why when you want the lens cover off while aclimating and THEN close it when it is done aclimating.[/QUOTE]

I should've thought of that, but didn't. Good point
Thanks for all of the insight and help everyone. Hopefully by trying a combination of the ideas and products, I won't have the fog issue again.

 

[Pinecone]

Yes, but if it is warmer than ambient, it means you'll trap warmer air, which can carry more moisture in it, between the lens cap and the lens element. As it cools down as you are aclimating the rifle/scope, that moisture will condense on everything.

This is why when you want the lens cover off while aclimating and THEN close it when it is done aclimating.

Yes, I agree with that.

But only if that warmer air has enough moisture that the dew point is above the ambient temp. I could trap 100F air in between the scope cap and the lens, and not get fog at 40F, IF the dewpoint of the 100F air is 35F.

The other thing is, there is not much moisture in the air that can be trapped. Do the calcs.

 

[lazarus]

Sure, but you could still get some layer for lens fogging. I've certainly seen it taking a camera lens from a warm, semi-moist environment, putting a lens cap on and then taking it off hours later after it sat in a cool environment. Even less air/moisture trapped with most camera lenses and caps than a scope cap.