Ammo & Gear Reviews

How Thermal Scopes Work


Guns and Gear Contributor
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By Joseph O’Brien,

Thermals scopes are by far one of the most interesting accessories that you can have on any pistol, rifle, or shotgun. Knowing how these work can really give you a good advantage in some applications, especially at night when there is no light within your immediate surrounding area. If you have no idea of how a thermal scope works or if you’re considering purchasing one and want to know a little more beyond the basics, then this brief guide will serve as a reliable source. We’re going to cover what kind of purposes these scopes are used for and how exactly they work.

What Are Thermal Scopes And How Do They Work?

Thermal scopes are not to be confused with night vision scopes, despite both being effective in low-light or no-light settings. The difference here is that thermal scopes are able to pick up thermal patterns. They are able to pick up heat signatures that are generated from humans and animals alike. Thermal imaging is one of three types of infrared light. The other two are near and mid-range. So how do the two differ?

Here’s what you need to distinguish between each one:

Near IR: In this instance, this is the closest you can get to visible light. If you’re using night vision scopes or optics, then they will rely heavily on this type of IR lighting. Although it matches the behavior of visible light, this is not visible to the human eye.

Mid-Range IR: This will have a longer wavelength compared to near IR lights. More of your night vision goggles (mostly your digital night vision goggles in particular) will respond more to this type of IR lights.

Thermal IR: Thermal IR wavelengths are the farthest away from visible light. It’s these IR lights that can only be picked up thermal scopes and optics.

What Applications Will Work With Thermal Scopes?

There are some applications that can be used with thermal scopes. It is important to know which applications you’re intending to use these scopes for. Here are some of the more popular applications that are often associated with thermal scopes:


Night hunting is legal in most jurisdictions (depending on the type of hunting that is allowed). When you’re in a low-light or no-light condition, animals will usually prowl the fields at night. These range from varmint and predators like foxes and coyotes to name a few. If you’re in an area where night hunting is allowed, be sure to check your local and state laws to know which game can be hunted at night and which ones are prohibited from night hunting. The last thing you want to do is unintentionally break the law and face legal headaches that no one wants to deal with.

Self-Defense/Home Defense

Yes, home invasions do happen at night. And it’s up to you to make sure that a prowler or burglar will think twice before committing the same crime again. These thermal scopes will work to your advantage on a pistol, shotgun, or rifle of choice since you’ll have little to no light to work with. And if you’re in the shadows and out of the view of the invaders, you have a pretty good vantage point to ward them off, if necessary.

The Pros And Cons Of Thermal Scopes

While thermals scopes have their advantages, they are not perfect in every way shape or form. They do have some cons of their own. The following is a list of the pros and cons of thermal scopes. If you come across one that you like and decide to purchase it, here’s what you might expect:


Surprisingly Useable In Any Lighting Condition

We’ll begin with the first pro on the list that will definitely surprise you: they don’t JUST work in dark lighting conditions. They can work in broad daylight. The reason why is that thermal scopes do not depend on any light at all in order to work properly. Thus, they can be used at any point in time day or night.

Excellent Range Of Detection

While some scopes won’t have a really good range at detecting heat signatures, there is a handful that will. A great thermal scope will be able to easily detect the heat signature of any target from hundreds of yards away. Granted, this is commonplace with more of the higher-end thermal scopes.

Cannot Be Hindered By Environmental Conditions

Put a thermal scope up against a regular scope with a rifle and see who wins in a contest between the two when it comes to optical images. There’s a guarantee that the thermal scope will work nine times out of ten every time. Why? A thermal scope can allow you to see through and get a good look at your target without any rain, smoke, or dust getting in the way. To top it off, it can actually see through some light vegetation and foliage. If you are able to see a target through some light bushes, then there’s a good chance you’ll have a better hit probability than any other rifle scope you’ve used period.

You’ll Know Where The Target Is And Their Previous Locations

While you can be able to know where your target is currently situated, you’ll also be able to see where the target recently was beforehand. However, these heat signatures from their previous location don’t stay around too long. If you happen to see heat signatures like this, there’s a good chance that something is close by.


These Scopes Come At A Price

With scopes equipped with this technology, it’s a given that they don’t come cheap. So if you’re looking to purchase one at some point in the future, you better have a good idea of how much you want to spend. Keep in mind scopes with better features (i.e. long -distance shooting) will likely have a higher price than those that don’t.

Some Are Large In Size

There are some scopes that are so large in size, they will make your rifle of choice look a little bulky. Not to mention, some of these scopes might be a little bit on the heavy side. So you’re looking at the possibility of adding on a little more weight to the rifle you choose.

ID’ing Your Targets Can Get Tricky

This is a risky situation, especially in a home defense application. You may not be able to tell the difference between a home invader or a member of your family. That’s why it’s absolutely important to try and safely get a positive read on your assumed target before engaging.

Final Thoughts

Finding a thermal scope will take some time and a little bit of work. It’s important to find one that will fit your intended needs and purposes. While looking for a scope, you should consider putting together a list of what you want out of a thermal scope (i.e.–How far out should it pick up targets?) This way, you can have a process of elimination to determine which scope will stick out as the best in the end.

Joseph O’Brien is a writer for He is a Certified Glock and Smith & Wesson Armorer in addition to being an Association of the United States Army Distinguished Scholar Award Winner. Click here to visit