[Reasons And Solutions] What Causes a Scope to Fog Up?

Regardless of the quality of the scope you are using, fogging can occur on the outside of scopes, as well as the inside. Most of the time, it’s simply because of the weather, however, lens coating plays a very important role too.

Fogging on scope lenses is a natural phenomenon that happens when the fog condenses on the optics. When there’s a temperature difference between the air and your scope lens, you will see fogging. At times, it can be very frustrating. Especially when you encounter fogging when you are about to engage.

Here in this article, we’ll explain what causes a scope to fog up and how you can prevent this.

Reasons Behind Your Scope Getting Fogged Up

Weather is not the only reason for lens or scope fogging, but it certainly is one of the main factors. Here are the most common causes of fogged-up scope.

1. Collection of Moisture

We typically store our hunting equipment in a cold and dry place. This is obviously the best place to store them but when you take them out to the world, which is usually warmer, the lower temperature on the scope optics causes it to get all fogged up.

This can happen too due to the low temperature of the air-conditioned vehicle which you used to get to the hunting ground.

2. Worn-Out Lens Coating

The lenses on your scope are usually coated in some sort of anti-fogging material. But as time goes by and you keep on using the scope, the coating gets all worn out. So, it can’t prevent fogging anymore. Also, the quality of the anti-fog coating has an impact too. It’s only natural that cheap lenses come with cheaper quality coating, which is not very effective, to say the least.

3. Parallax and Magnification

Looking through the scope, if you encounter foggy and blurry images, there’s a good chance that you’ve fallen victim to the infamous parallax effect. The relative position of the target can change due to your body movements, or simply with your scope movement, especially when there’s a busy background. This causes a parallax effect, which leads to foggy and blurry vision.

4. Faulty Scope

If you encounter fogging and can’t seem to wipe it off, there’s a good possibility that your scope has accumulated moisture inside. A worn-out or faulty scope can be the reason for this. A compromised seal between the scope lenses will lead to moisture getting trapped up and eventually, molds will develop.

Fixing Your Fogged-Up Scope

Fixing a fog-ridden scope, depending on the situation, can be quite easy. Here’s what we recommend.

1. Allow some time for adjusting the temperature of your scope and the outside environment.
2. Don’t breathe directly onto your scope. Because our breath, which is usually warm, can lead to differences in temperature between the scope and outside, leading to fogging.
3. Always buy good quality scopes that are anti-fog certified by the manufacturer.
4. If you have worn out the anti-fog coating, treat your scope lenses with a good-quality anti-fog coating solution.
5. Maintain your scope at regular intervals with proper lens cleaner.
6. If you see fogging on the inside of the scope, send it for replacement or get it cleaned by a professional.

Frequently Asked Questions And Answers

Will rubbing alcohol keep glasses from fogging up?

No. Rubbing Alcohol is a good cleaner, but it has no anti-fogging properties.

Can you get the moisture out of scope?

No. You need special equipment and trained professionals for that.

Can you use Windex on a scope?

No. Using Windex on a scope is not recommended. As it can damage the coating on the scope lenses.

Why is my spotting scope blurry?

Spotting scopes, just like regular scopes, can get blurry due to moisture build-up on the lenses.

Summing it Up

Be patient, as it’s the key here. Because, most of the time, your fogged-up scope will clear itself within a few minutes. Take a dust blower with you if you encounter too much fogging, to blow fog and dust off the lenses from time to time. Wiping with a piece of microfiber cloth can help too. Adjust the focus to your comfort beforehand. Most importantly, don’t attempt any DIY repair, as you’ll end up destroying your precious scope.