The Best Thermal Clip-On Sights

In theory, clip-on scopes should be the thermal that every hunter wants, needs, and easily deploys. These are accessories to traditional rifles and daylight scopes, and if they don’t exactly “clip on” to those scopes, they clamp, screw, swage, and otherwise connect well enough to render your dad’s deer rifle into a next-level night-hunting rig.

In theory, they enable a hunter to have it all. With the clip-on detached, use your rifle as you ever have. But with the thermal in place, you can hunt the night. Your daylight scope’s zero doesn’t change, and you don’t have to invest in a spendy and specialized thermal rifle and dedicated night scope to get into nocturnal hogs and predators.

But theory is for dreamers. In our experience, confirmed in this year’s test of a half-dozen of the year’s new clip-ons, these devices don’t easily or adequately connect to a scope. They have disappointing resolution, and aligning the thermal’s reticle and image plane with that of the scope is frustratingly hard, especially when you combine optical and digital magnifications. Our conclusion, at the end of a half-week of field testing, is that while clip-ons promise plug-and-play utility, as a class they have a learning curve that’s steeper than that of dedicated thermal scopes.

The reason makes sense, if you think about all the variables that have to align in a clip-on. You have to adjust the magnification of the daylight scope (we call them slave scopes in this article) to fit the field of view of the clip-on. Then you have to match the focus of your slave scope with the display of the thermal. For those clip-ons with digital reticles, you then have to either align the thermal reticle with that of the slave scope or you have to override the slave scope with the digital reticle. But that’s not ideal; having two reticles in the same image is visually confusing.

If you use the digital reticle, you then have the added task of zeroing that reticle to your rifle.

Whew. That’s a lot of alignment, and can frustrate those hunters who buy the theory that these are plug-and-play devices.

All those cautions aside, the value proposition of a clip-on makes it worth the time and cursing to mate it to a slave scope. Because, when it works out, this handy, versatile, and powerful accessory really can convert your traditional rifle into a night-seeing powerhouse. And, when you’re done hunting the night, you still have your traditional daylight scope and rifle, same as it ever was.

The sharp, smart, durable, and easy-to-use clip-on was not only the standout winner of the category, but it gets double points for being a very good thermal viewer when it’s not attached to a rifle scope. Triple points if you consider that it is a decent daylight sight as well as being a clutch nighttime optic.

The tri-purpose talents of this instrument help justify its $5,700 price, but the ability to scan surroundings with the hand-held Calonox 2, and then quickly attach it to a riflescope to make a shot is one that we confirmed, to our satisfaction, earlier this year at our testing grounds in Texas. After a couple of dry runs to make sure that all the connecting clamps and threads were ready, we managed to transition from viewer to sight in under 30 seconds. Users with more practice could cut that time in half.

That versatility also makes the Calonox 2 a good choice for hunters who want to use the unit with different rifles. As long as the sold-separately Rusan adapter fits the objective bell of your daylight scope, the Leica can be swapped easily and quickly between platforms.

I hasten to note that the Calonox 2 is mainly a clip-on sight; its utility as a viewer is limited by its 1x magnification, its display that can’t be adjusted for individual users’ optical prescriptions, and by a tiny screen that looks to be at the far end of a long tube.

Of course, all those display shortcomings are negated when affixed to a slave scope. We used Leica’s bright Amplus 6 3-18×44 partly for brand coherence but also because the reticle is simple and the configuration so useful for mid-distance predator hunting. Later, we used the Steiner Predator 4 4-16×44 scope to further confirm the Calonox’s talents as a switch-hitter.

One of the frustrating aspects of using clip-on thermals is calibrating their screen dimensions and aligning their reticles to that of the slave scope. Because the Calonox doesn’t have a digital reticle, that hassle is obviated.

“Of all the clip-ons, it was by far the easiest to set up and to use,” said tester Derrick Ratliff, who noted that the Calonox 2 has an awkward shape that doesn’t easily fit in hand when used as a monocular.

Among the qualities that gave the Leica top scores is its robust build, its short 6-inch length that makes reaching its controls a cinch even on longish slave scopes, and its intuitive three-button operation. We also liked the easy operation of its laser rangefinder, the lens of which is in the right wing of the unit (the left wing contains the internal rechargeable battery). A long press of the rearmost button lights up a bracket in the display. Bracket your target and a short press of the same button gives you the range. We couldn’t get the 2,400-yard detection range, but we could easily recognize and range deer- and coyote-sized targets inside 500 yards.

We also liked the generally crisp and bright image delivered by the clip-on, at least through magnified scopes. Images captured by the unit are generally good, and Leica’s new Calonox View mobile app is a big improvement from its previous iteration.

Among the Calonox’s demerits are a generally dim display at night. This attribute cuts both ways, as more subdued displays are easier on the eyes, but because we ran other clip-on units at a higher intensity, the Leica unit seemed dark and slightly fuzzy in comparison.

We also quibble a bit with the price, which is fairly stiff for a clip-on. Units without the laser rangefinder run about $1,000 cheaper. Leica has introduced an 840×640 version of its Calonox viewer, so a similarly high-resolution version of the clip-on thermal might be on its way.

But this 640-class unit is perfect in just about any way, and easily won our Editor’s Choice award for top clip-on with its effortless operation, versatility, and durability.

With a robust metal build, smart 4-button navigation, and the ability to function either as a clip-on paired with a daylight slave scope or as a stand-alone thermal sight, this compact unit might be the most versatile and useful of Sig’s new thermal line.

While the rail-mounted ECHO SV-LRF rifle sights have a little more reach and optical performance, thanks to 50mm and 35mm objective lenses, the little 25mm CV25 packs a ton of features in its 5-inch-long frame. They include navigation buttons that can be customized, recoil-activated recording, and a very good 640-class thermal sensor.

The normal connection between slave scope and clip-ons is achieved with an adapter that screws into the eyepiece of the thermal and then clamps onto the objective bell of the slave scope. The arrangement does a good job of making a light-proof connection between the two optics, and the clamp can accommodate a narrow range of objective lens diameters. But it’s slightly terrifying, since it requires hunters to hang a heavy and bulky optic to the objective bell of their daylight scope.

The alternative is to add a rail mount to the thermal, which addresses the issue of hanging the clip-on from the scope, but adding equivalent mount height to the list of variables to consider when mating a clip-on to a daylight scope defeats the whole purpose of a clip-on, which is to be a drama- and hassle-free add to your normal daylight rifle set-up.

Thanks to the Sig’s integrated quick-detach rail mount that’s precisely 1.535 inches high, the unit aligns perfectly with an LPVO or similar scope with a 30mm or smaller objective lens on a standard-height unimount. But here’s the rub. The two optics nest together so tightly that you may need to adjust the scope inside its mount in order to ensure that no ambient light gets between the slave scope and the thermal.

You’ll need plenty of real estate for this tandem set-up, a consideration that makes the ECHO SV25 a perfect match for an AR platform. There’s simply not enough rail room on a standard bolt-action receiver for both the slave scope and the clip-on, but ARs have ample rail dimensions.

Sig doesn’t really publicize the SV25’s greatest feature: it can operate as clip-on, relying on the reticle of the slave scope for its aiming point. But it can also run as a stand-alone thermal sight, its digital reticle the aiming point for this purpose.

We ran it in both modes, and its 1x base magnification and display are optimized for use with the slave scope (we used both Leupold’s Mark 5HD 2-10×30 and Sig’s TANGO-MSR 1-10×26). In sight mode, the display appears to be located at the bottom of a deep well, and the 1x magnification limits its use to inside 100 yards. It’s not a bad hog thermal, and works okay for personal-defense purposes, but when it’s in clip-on mode, the reach triples and the full array of its features comes to the fore.

The unit doesn’t have a rangefinder, either a laser-guided model or a stadiametric version that uses relative sizes of targets to determine their range. And while the ECHO connected to Sig’s BDX app and device connectivity ecosystem, we struggled to wirelessly transmit videos and photos through the app. But we transferred images easily via a USB cable.

 Despite those shortcomings, the SV25 delivers most of the features you’d expect from a thermal from Sig, and given its wide versatility and robust build, it’s worthy of the brand, and your attention.

Read Next: Best Thermal Monoculars

It’s an imprecise demarcation, but thermals can fairly be divided into “hog” units and “coyote” thermals. The former are engineered for fast shooting inside 200 yards. The latter have attributes for the longer-range precision shooting often required of nighttime coyote hunters.

To add an additional squishy differentiation, most hog thermals are at home on AR-15 carbines while coyote thermals are optimized for flat-shooting bolt guns like the 22 Creedmoor, 6mm ARC, and 6mm Creedmoor.

The German optics brand Liemke has developed a stellar reputation in Europe for thermals designed for nighttime boar hunting, but its new top-end Luchs-2 extends its reach. It’s an excellent unit for high-seat roe deer and sika deer hunting in Europe and mid-range coyote hunting in the States.

“Built like a European sports car combined with a 4×4 pickup,” wrote tester and OL’s gear editor Scott Einsmann of the Liemke’s tight build and responsive operation.

Functionally, the Luchs family of thermals is simple and fast to operate, even with gloved fingers. The three navigational buttons are large and distinct, and once you get the hang of their functions, you can play this thermal the way an Army bugler plays his trumpet. We liked the easy-on-the-eyes display, and its function lever that toggles between off, on, and battery-saving standby mode.

While we used the Luchs-2 as a clip-on, paired with the excellent Minox RS-4 in 2.5-10×42, the unit is a decent hand-held viewer. That versatility gained the unit additional points, but the Liemke shines as a clip-on partner to a capable slave scope, mainly because its 640-class sensor seems to cut through the dark better than other units in its class. While its 2,500-meter range may be a little generous, we were able to mark and identify targets out to 1,000 yards, making this an excellent coyote-range clip-on.

Demerits include the lack of a rangefinder, but that’s not a huge detraction for most hunters. And, at almost $6,500, it’s pretty expensive for a clip-on, even one with wide versatility.

But we gave the Liemke cred for its robust build and its serious manners. While many thermals can feel as plasticky and janky as a video-game console, the German-made Luchs-2 has the feel and behavior of an investment-grade European optic. 

Best Budget Rangefinding Clip-On: Guide TB630 LRF

This little unit from Guide is chock-full of features, from a laser rangefinder to all the standard palettes and modes you’d expect, plus a very good mobile app to receive photos and videos, all inside a tight, durable metallic housing that can be rail-mounted in front of a slave scope or clipped directly onto the daylight scope. Add its impressive 10-year warranty, and the sum of all these parts is an excellent value for under $3,300.

I know. That’s still a shocking amount of money for a gun-mounted electronic. But the Guide has features that are generally reserved for thermals in the $5,000 class. They include a true laser rangefinder, instead of the bracketing range-finding feature called stadiametric that is used in most entry-level thermals.

The Guide is also built for abuse. It has 2-meter shock resistance and is rated to be waterproof. We didn’t test that durability standard, but it’s comforting, given all the abuse night hunters dish out to their gear. When you consider Guide’s 10-year warranty, twice the industry average, that’s a lot of consolation for the price.

Because we lacked a good adapter for our slave scope, we rail-mounted the Guide ahead of a daylight scope, getting the two optics in tight collimation. That’s not ideal, since any ambient light between the two units can degrade the image, but happily Guide lets users mount the way we did, with the 1.5-inch-high quick-detach rail mount, or by using an adapter for an unsupported connection to the scope. Again, that’s a lot of versatility for the price.

We liked the ambidextrous side focus controls that accommodate both right- and left-handed shooters. Battery swapping is a cinch with the single 18650 cell, and the TargetIR app is easy to use to accept video and photos from the unit.

We did have a few gripes. First, the left-side menu buttons are hard to navigate, especially for thermal natives who are used to buttons on the top. And pushing on the side of an optic can move it off target. We reckoned the useful range of the TB630 is about 250 yards, which makes it an excellent hog thermal but a little anemic for long-range predator hunting.

Still, those are minor quibbles. The Guide TB630 is as robust a build and as solid a bargain as you’ll get in a thermal clip-on.

See It

Pros

• At 5.2 inches and .9 pounds, compact form factor
• Decent dual use as handheld monocular
• No zeroing or calibration required
• 3-button menu navigation
• Uses standard 18650 batteries
• At under $3,000, an appealing price

Cons

• Disappointing range
• No photo/video capability

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Key Features

• 
  Price:

  
  $2,995

• 
  640×480 thermal core

• 
  1024×768 OLED display

• 
  12-micrometer pixel pitch

• 
  60 Hz refresh rate

• 
  2,800-yard detection range

• 
  1x base magnification, 2x and 4x zoom

• 
  8-hour run time

• 
  5-year warranty

• 
  Quick-detach rail mount

You may note that we aren’t awarding a Great Buy in this particular category this year. That’s because there’s no raging bargain in this collection of thermals whose starting price is a cool $3,000.

But the surprisingly effective TICO LTV 640 from ATN comes close to being a great buy. Along with the Burris, it’s the lowest-priced clip-on in the collection, it can be used as either a scope-mounted clip-on or a hand-held monocular, and it has excellent resolution.

If it also had photo and video capability, plus a Bluetooth connection to a mobile app, as nearly all of its peers have, this would have been the consensus Great Buy of the category. But lacking those, and also a rangefinder, held it back in our collective judgement.

What the TICO does have is straight-forward operation and a surprisingly good image for such a square, clunky-looking thermal. Its thermal-enhancement feature can further boost the image in various light and humidity conditions. We also like its big, grippy objective-bell focus control, which makes tuning up images fast and easy.

Like other clip-ons in the test, the ATN has a removable quick-detach rail mount. We didn’t have a scope adapter that fit our daylight slave optic, so it was a life-saver to have this 1.5-inch-high mount to use the TICO as intended. The thermal fits closely to the slave scope, with very little ambient light degrading the image. But a correctly sized clip would further boost the versatility of this smart little scope. But the rail-mount mode makes the TICO quick and easy to deploy and then to remove, as needed.

We also used the ATN as a hand-held thermal. The unit has a nifty feature that changes the size of the display depending on whether it will be used as a 1x clip-on or a hand-held. The unit worked well in either mode, but it’s better suited as a companion to a daylight scope. The ATN’s display can easily be tuned to the image plane and field of view of the slave scope.

In all, it’s a great and simple option for most uses out to about 300 yards. If you’re after a TICO at an even more accessible price (though with less resolution), consider the 256-microbolmeter unit for $1,095 or the 320-class clip-on for $1,795.

Of all the traditional optics brands, Burris was an early and enthusiastic player in thermals. It makes sense, since the company’s sister, Steiner, hails from Germany, which has its own robust tradition of thermal sights for low-light and no-light hunting.

Burris’s freshman clip-on, the v2 version of the BTC35, was (and still is) useful and will get hunters out after dark. But while the v3 version of the clip-on shares many specs, including thermal core and display resolution, the new iteration hits harder, with better app connectivity, a fast and intuitive rotary control system, and the ability to swap batteries in the field without shutting down the unit.

The resolution of the BTC35 remains a little anemic, and the entire unit has a lightweight, plastic-y feel. That’s not all bad, as the light build doesn’t imbalance a gun and doesn’t hang a ponderous amount of weight from the objective bell of the daylight slave scope. But compared to, say, the Armasight or the Guide clip-ons, the Burris feels flimsy.

Its 400×300-microbolometer sensor limits its reach, but we found that it’s plenty useful inside 200 yards. The Burris’s dizzying number of features allow users to customize its nine palettes, display contrast, picture-in-picture mode, stadiametric ranging, and hot-spot tracking. Riffing between all these menu choices is a cinch with the Burris’s rotary dial system. Push the knob for either a short or long pulse, then dial your way to the screen and function of your choice. It’s a fast and intuitive navigation system that we wish more brands would adopt.

We also like the easy connection to a daylight slave scope. We used Burris’s Smartclip Adapter, and found it easy to mount and dismount. We used a 1-6×24 LPVO as our slave optic, and the Burris, with 1x base magnification and zoom capable up to 4x, was a perfect companion for that platform.

The v3 version of the BTC35 has a better power plant than the v2 generation, and the twin top-loading battery compartments are easy to access. But the rechargeable CR123 batteries limit its run time to about 4 hours, though the rechargeable batteries can be topped off between stands.

Connectivity to the excellent BurrisConnect app is good, though we had trouble with an unstable Wi-Fi link to our device. In our field testing in Texas we struggled with aligning the digital reticle with our rifle’s zero, but back in Montana, with more time and patience, we managed to work through the interface to collimate the two optics.

That experience is telling of the Burris’s personality. It makes up for middling resolution and durability with very good software and navigation. Plus, its 1-pound weight and compact build makes it a handy thermal to tuck in a jacket pocket that’s easy to deploy when your outing takes you long past sunset.

Owing to its long involvement with providing gear for military customers, Armasight’s thermals are built for the battlefield. The Operator, Armasight’s compact and versatile consumer-grade clip-on, is no exception.

The 630-class thermal is protected by a durable aluminum alloy housing and its controls are weatherproof. Its battery compartment and micro-SD slot, used to record media, are both tethered with tiny cables to make sure the caps don’t get lost. The form factor of the Operator, a compact 6 inches long and weighing just a pound, makes this a pocket-sized companion that easily snaps into use thanks to its quick-detach rail mount.

Further confirming its field chops, the three-button operation is fast and intuitive to use, even in total darkness and in high-stress environments. The ArmaCORE thermal sensor, interface, and even display features are shared across the Armasight thermal family, which includes the Warden thermal monocular and Contractor weapon sight. Once you get familiar with the operation of one, it’s a cinch to switch platforms.

While the Operator is an honest clip-on, and mates nicely with an LPVO daylight scope, we found it lacking in a number of features that consumers have come to expect from the class. The Armasight records both video and photos to a sold-separately SD card, but in order to transfer them to a device, you’ll need a USB-C cord. Like other thermals in its family, the Operator is powered by a pair of CR123 batteries. The good thing: they’re readily available. The bad thing: their 4-hour run time is fairly anemic compared with what’s becoming the industry-standard: larger 18650 cells.

All that said, the Operator delivers a rich and contrast-y image, and it’s easy deployment and operation makes it a quick and critical addition to a daylight scope. We like its handling at its 1x base magnification, but its 1024-pixel display delivers a nice image at 4x, as well. If you’ll be hunting in miserable weather, in situations where your gear will be abused, the Armasight Operator is one of the best clip-ons in the category.

How We Tested Thermal Clip-Ons

We tested this year’s class of thermals in the places and style that most American hunters use them: in Texas hunting coyotes, bobcats, and wild hogs.

We based our test out of a sprawling ranch in South Texas’s brush country, where we had thousands of acres of coyote and bobcat hunting out the back door. We also had access to a shooting range with steel targets out to a mile and reaction targets from Arizona’s MR Target.

We used a combination of Horizon Firearms bolt guns and ARs chambered in 22 Creedmoor for most of our clip-on testing. One of the important considerations for this class of thermals is that most require a full-length rail for mounting. We mounted those clip-ons with appropriately sized adapters directly to the objective bells of slave scopes. Those with independent rail mounts were mounted ahead of the slave scope.

When possible, we shot with the daylight optic at a bench, then slapped on the clip-on and assessed the connection between the two. But we also assessed the interaction between the two. Did the slave-scope’s zero change? Did the clip-on have a digital reticle that needed to be zeroed and/or calibrated with the scope’s display.

We used the stationary targets as the basis for assessing thermal image, sensitivity, focus, and operating range.

But the bulk of our testing was in the field. Test team member, competitive coyote hunter, and captain of “Team Dead On,” David Stroud, provided his high-rack rig with three swiveling shooting tables. While Stroud drove, the rest of the team rotated through sessions on the high rack and with various thermal sights and viewers. In quiet moments between calling sessions, we cycled through thermals’ menus, practiced navigating their buttons and features in the dark, and assessed image quality, various features like rangefinders and color palettes, and recorded videos and photos through the devices.

And we killed coyotes and bobcats, enough to confirm the talents of many of the submissions in real-world conditions. Our plan was to take the collection of thermals to a neighboring ranch for a night of pig hunting, but while we were in South Texas, a monsoonal rainstorm broke the region’s drought, and we were washed out of pig hunting. But Stroud later took many of the thermals to a hog lease, where he finished evaluations and content collection.

In daylight, we further evaluated the units, rating them on ease of use, connectivity to a mobile app, versatility for a wide range of uses, thermal features, image resolution and overall image quality, and durability. And we assessed their value, asking of each submission: how much performance do you get for the money. This particular category, considering thermals can cost several thousand dollars, is among testers’ (and buyers’) most important considerations.

The unit with the highest overall score wins our Editor’s Choice as the best submission in the category. The thermal with the highest Price/Value score wins our Great Buy award.

The Outdoor Life Thermal Test Team

This year’s Outdoor Life thermal test team includes a pair of Texans who handle more thermals in a month than most of us do in a year and three Outdoor Life editors who evaluate gear with a combination of objectivity and close attention to detail and value to readers.

Texan David Stroud actively participates in the growing competitive coyote circuit, hunting all night across Texas at least a couple weekends a month and using a wide variety of thermal viewers and weapon-mounted sights in his pursuit of fur and prize money.

Derrick Ratliff is the founder and president of Horizon Firearms in Bryan, Texas. Ratliff was an early adopter and manufacturer of the 22 Creedmoor, a round that’s become a darling of night hunters for its flat trajectory, mild recoil, and hard-hitting performance on predators and hogs. We ran Horizon’s bolt guns chambered in 22 Creed, fueled by Hornady’s 80-grain ELD-X ammunition.

Alex Robinson is Outdoor Life’s editor in chief and frequent member of OL’s gun and optics tests. He’s an avid deer, turkey, and waterfowl hunter and is relatively new to hunting with thermals.

Scott Einsmann is Outdoor Life’s gear editor, and oversees all of OL’s flagship gear tests. As the youngest member of the test, he’s also a digital native, an important consideration for navigating thermal devices.

Andrew McKean is Outdoor Life’s optics editor and designed our test methodology as well as handling most of the testing logistics.