Scope fogging up late in the evenings in south Ga.

[GEWDOIT]

I live in southeast Ga. We have humid weather even in the fall. It might be 30 deg. but still not a dry cold but a wet cold. Scopes fogging up late in the evenings(last 10 min of legal hunting) is a major problem. Any suggestions on a good low light-no fogging scope form  $75-$150 tops. I've read 400 reviews on products from bass pro,cabellas,walmart etc.. and one guy loves a scope the next guy will say it fogged up and ruined his hunt.

[PowPow]

its not a product problem; the simple physics is the surface temperature of theglass gets below the dewpoint of the air and water condenses on the surface. happens to scopes, the inside of car windshields in the winter, the outside of car windshields in the summer, glasses of sweet tea...

try keeping the end bells warm with your hands while you sit there. sometimes I tuck the scope under the end of my jacket with the rifle laying across my lap. if the glass is any bit warmer than the dew point of the air, it should not fog up.

and don't do what I did once when a big doe walked by; exhale as you are putting the gun up to shoot. your breath has a very high dewpoint.

[GEWDOIT]

Thanks, I'll try all those suggestions, they all make pretty good sense.

[mechanic]

Pick up some rain x at the auto parts store, and follow directions to clean and coat the lenses.

Ben

[possume]

i wouldnt try keeping warm with hands that will make worse.the scope needs to be same temp as the air or it will fog for sure. is the fog inside or out if inside it has leaked the gas out of the scope aqnd needs to be recharged

[PowPow]

i wouldnt try keeping warm with hands that will make worse.the scope needs to be same temp as the air or it will fog for sure...

then why do they put those heater wires in the rear windows of cars to heat the glass to defog it?

here is a reference on the science, see strategy #4 about warming the glass:
http://www.dctech.com/physics/features/0103.php

if the fog is on the inside, you would have to keep the glass very warm. then when the weather has been very cold for several days, you can open it up and let the very low dewpoint ambient air drift in, then seal it up. If you have access to dry nitrogen, purge it when dry nitrogen then seal it up.

Another short term solution would be to wrap hand warmer packs around the bells with rubber bands to keep the glass warm.

[possume]

the defrost is constant heat and when it goes off if the air in the car is still cold it will fog over again correct and it will stop when the air temp gets the same right. but its made to defrost wich isnt the problem we have here its humidity ive tryied kepping scopes warm but as soon as you remove the heat they fog so thats why i dont do it be in a warm blind open window to shoot scope fogs why different temps make it fogs over it like wearing glasses and be out in the cold for a while and walk in a warm house or car you get fogged over same as being in a cold place and walking out into a warm place you get fogged over

[possume]

the hand warmers on the bell will work because it is constant heat and will keep the moisture away

[PowPow]

the defrost is constant heat...

I have been in the industrial cooling and dehumidification industry for 25+ years, and get called on to solve similar condensation problems, although its on a larger scale. In that time, I have never come across an explanation such as this, but I will certainly ponder it for a while.

In my experience, the heat does not have to be constant, but once its removed, the scope starts cooling off.
Does it cool off below the dewpoint before you get the shot off? Depends on how warm you kept it.
The scope would need to be kept warm right up to the point the gun were raised to shoot.

And if you breath on it or around it, you will introduce humid air, so its important to exhale away from it and at a velocity that is higher than normal to promote mixing with ambient air, i.e., blow down and away.

An enclosed space such as a shooting house can retain heat,  but it can also retain moisture (humidity given off by your breathing) so the dewpoint in a shooting house can get a little higher than outdoors, which means your scope needs to be kept a little warmer.

[SHOOTALL]

Heat transferes from hot to cold . In this case the heat in the air is being transfered to the scope causing condensation much like a cooling coil in air conditioning. When the heat in the scope exceeds or equals the air temp the transfer will stop as will the condensate problem. A chemical ansewer would be some good anti fog solution to treat your lenses . I would suggest you try a welding supply store , winter welding out side can cause the same problem on shield lenses .

[charles p]

Dewpoint is a function of heat and relative humidity. Here is what I have experienced in the field.  I've found that whenever I kept the eyepiece of my scope under my armpit or coat, it gets warm.  Warm air can hold more moisture and will not easily fog.  Whenever I remove the scope from its warm environment, it cools quickly and cold air cannot hold as much water, thus it fogs immediately.

I have resulted to inserting a wad of tissue paper into the eyepiece to catch drops of rain, but not warm the scope.  With the muzzle pointed slightly downward, droples on the bell end of the scope are not a problem.  When I need to use the scope I remove the tissue, and without exhaling onto the lens, move the scope to the shooting position.

Works for me.

[tman1965]

The rain x trick will work... as does nikon's antifog wipes.

[helotaxi]

Bushnell Elite scope with RainGuard.  The 3200 3-9x40 is on sale at Natchez right now for $140.  Good glass, won't fog.

[williamlayton]

THIS is really off-topic and I apologize beforehand.
Russian snipers kept snow in their mouths so as not to give away their position when breathing----that was at Stalingrad.
Blessings

[Savage .250]

I`m sure that`s happened to a lot of scopes.  Not a failure (if it`s outside) but rather a nornal reaction to    the air/temp/surface conditions at the time.   As stated by others.
   Has happened to me as well. Just pay attention and when it occurs, wipe the lens clear.