What is a Thermal Sight?

A thermal sight, sometimes called a thermal scope, is a type of riflescope that doesn’t rely on visible light at all. Instead, it shows you heat. Every animal, person, or object gives off heat energy, and a thermal sight detects that invisible radiation, then turns it into an image you can see on its display.

This is different from a night vision riflescope. Night vision needs at least some light—whether it’s from the moon, stars, or an infrared illuminator—to brighten the scene. If it’s completely dark or the target is hidden in heavy cover, night vision struggles. Thermal sights don’t have that problem. They work in total darkness, through brush, smoke, and even fog, because heat always shows up, no matter the lighting conditions.

For hunters, that means a coyote slipping through tall grass or a hog rooting under heavy cover can still be seen clearly with thermal, while night vision might miss it. For security or search-and-rescue teams, thermal sights can reveal people in places where a traditional night vision scope would leave you blind.

Key Specifications of a Thermal Sight

When you start looking at thermal sights, it’s easy to feel like you need a science degree just to understand the spec sheet. Terms like “NETD” or “pixel pitch” don’t exactly explain themselves, and most hunters just want to know: Will this scope help me see my target clearly in the field? That’s fair.

The good news is you don’t have to master physics to make sense of these specs. Each one connects directly to something you’ll notice in real-world use—how far you can spot an animal, how sharp the image looks, or how well the scope holds up in the cold. 

1. Detection Range

On Pulsar thermal sights, you’ll see a listed detection range—sometimes over a mile on high-end models. Detection simply means the sensor can tell that a heat source is present at that distance. For example, a Thermion 2 LRF XL60 thermal riflescope might detect a large animal out at a maximum distance of 3,062 yards.

It’s important to know that detection doesn’t always equal a clear picture. You may be able to tell that “something is there” at maximum range, but to truly tell whether it’s a hog, a coyote, or a person, you’ll usually need to be much closer. The true usable distance depends largely on conditions like weather, terrain, and target size.

That’s why detection range is best thought of as the outer limit of what the scope can pick up, not the distance at which you’ll make a confident shot.

2. Sensor Resolution vs. Display Resolution

One thing that confuses a lot of people when shopping for a thermal sight is that it doesn’t have just one resolution—it has two. That’s very different from a phone or a TV, where you only ever see a single resolution listed. With a thermal sight, the sensor has its own resolution, and the display has another.

The sensor, also called the detector, is what actually collects heat information. In the Pulsar Thermion 2 LRF XL60, the sensor resolution is a massive 1024x768 pixels with a 12-micron (µm) pixel pitch. In practical terms, that means the sensor can capture very fine differences in heat, giving you more detail at longer distances. A tighter pixel pitch (like 12 µm instead of 17 µm) means the pixels are packed closer together, which helps you see small shapes and edges more clearly.

The display, on the other hand, is the screen inside the scope that you look at. In the XL60, it’s a sharp 2560x2560 AMOLED display. AMOLED (Active Matrix Organic LED) technology gives you brighter contrast, vivid thermal palettes, and faster refresh rates—so moving animals don’t blur and the image doesn’t wash out in the cold.

Together, these two resolutions explain why the XL60 gives such a crisp picture: the sensor captures more thermal detail than most scopes can, and the high-resolution AMOLED display shows it back to you in a way your eye can actually use.

3. NETD / sNETD (Noise Equivalent Temperature Difference)

NETD is a measure of how sensitive the sensor is to tiny differences in heat. It’s measured in millikelvins (mK). A lower number means the scope can see smaller temperature differences—like spotting a rabbit against warm ground.

• NETD is just the sensor rating.
  

• sNETD (system NETD) measures the sensitivity of the entire scope, including optics and electronics.
  

When comparing models, a lower NETD or sNETD means a clearer, more detailed thermal image, especially in bad weather when everything is closer in temperature.

Final Thoughts

Understanding the specs on a thermal sight doesn’t have to be overwhelming. Detection range, sensor resolution, display resolution, pixel pitch, and NETD all connect directly to how the scope performs in the field. For hunters, that means spotting game more reliably. For landowners, it means better security and peace of mind. And for professionals, it means dependable clarity no matter the conditions. By focusing on what these numbers actually mean in practice, you’ll be able to choose a thermal scope that gives you the confidence and performance you need when it matters most.