Double Vision

‘Multispectral’ was the buzzword at the 2023 Great British Shooting Show. It means bringing together some combination of daylight, low-light (IR), and thermal optics (and arguably laser-range finding) in a single device, and it aims to harness together different slices of the electromagnetic spectrum to create more effective devices. Sometimes, its goal is to overlay the resulting images on one another, creating what is known as ‘fusion’. This is an exciting trend, but a big technical stretch. More practical, is ‘channel-switching’, which is the ability to select the slice that gives you the information you need from moment to moment.

Pulsar has been working hard to integrate extra spectrum slices into its products. In their Digex C50 digital riflescope, they have added full-colour daylight functionality to what had previously been a dedicated NV unit, to give the user a device that operates seamlessly around the clock. Plus, they have upgraded the firmware of their laser-rangefinder-equipped thermal riflescopes to work with their new smartphone-based ballistic programmer, so that moments after ranging their target, the shooter sees the required holdover shown in the reticle.

A step forward

Complementing these devices are the Thermion Duo DXP50 and DXP55, which enable the user to switch at the press of a button between a thermal image generated by a super-sensitive 640×480, 17µm, <25mK NETD thermal sensor, and a daylight image delivered by a high-definition 4K (3840×2160px) CMOS, or to selectively combine the two using the picture-in-picture (PiP) facility. The European-made thermal sensor is fed by an equally high-spec, 50mm objective lens, with an optimal f.1.0 focal length, and top-quality germanium glass. Thereafter, its output is rendered visible by Pulsar’s image-processing algorithm. This is a stage that barely registers in specification tables but is crucial to how the sight performs, and for my money – literally - it is the best there is. Moreover, Pulsar’s regular firmware updates mean that whenever their boffins find a way to improve it, the user gets a free performance boost. And since there’s little point in optimising processing unless you can do justice to the results, the DXPs are equipped with a 1024×768 HD AMOLED display. You will find displays with higher pixel counts in other brands, but as these are filled by the image processing ballooning out the data from sensors that are themselves less refined, the information they provide is significantly less accurate. A final often-underappreciated component is the eyepiece. This magnifies the display to show it in optimal detail and from the widest possible angle (29.5° in this case) to make it quick to acquire and comfortable to use for extended observation.

Daytime

Now for the daylight camera. On first hearing Pulsar’s plans to offer a combined day/thermal scope, I imagined a C50 with a small thermal unit on top, so something that would let you reacquire whatever you had picked up in your thermal spotter and get a better look at it in colour or IR. But Pulsar has flipped this. This is because they are (a) smarter than me, and (b) have to deal with the practical realities that make a thing work! You see, although thermal imaging may seem like magic, it requires some precisely arranged high-end hardware, and that requires significant space. By contrast (as everyone with a smartphone knows), daylight imaging can be impressively miniaturised. Thus, in the Thermion Duo, Pulsar has given us a powerful thermal riflescope supplemented by a capable daylight camera mounted in a pod on top of the objective bell. The lens of this camera has a seemingly unimpressive spec of F35/4.34 with a fixed-focus format. But again, real-world performance shows Pulsar’s design expertise, as you get impressive clarity and detail with no extra focus dial to fiddle with. To be fair, sub-20m the focus isn’t as good as it is at longer ranges, but if that bothers you, you can simply switch to thermal, use one of the handily ambidextrous knobs on either side of the objective bell to focus the big 50mm lens, and have all the close-up clarity you want. As well as being lightweight (60-grams) and compact (only 0.5mm higher than a standard Thermion), the camera pod is equipped with a sliding 2-part lens cover that can act as an aperture-reducer to reduce glare in really bright conditions, though full adjustability is naturally provided via the brightness and contrast controls built into the scope. Predictably, one of the first questions I asked myself about the daylight camera was “Will it work with an illuminator as a digital NV system?” Equally predictably, the answer is “No”. In a darkened room it dimly detected the IR on the far wall, but that was it. In the field, the illuminator had no perceptible effect, and the camera lost colour and then definition well before the naked eye. At around 22:00 hours on a July evening, a muntjac I could see clearly at 80m disappeared into a fizzy grey blur when I looked for it in the Duo. So, I tapped the handy channel-selector button at the rear of the ocular bell and re-acquired it instantly. Interesting, too, is how marked the threshold is. The next evening, and just 20 minutes earlier, I was able to record a roebuck in full colour and good definition. Yet soon after he disappeared from view, the camera went to monochrome, and 5 minutes after that, the image was unworkable. Conclusion: The Duo is a fantastic night sight, but in thermal mode only! The great discovery is how transformative it is to be able either instantly or constantly to supplement the daytime channel’s detailed, full-colour, zoomable image with the thermal image by day. This means no more fruitless searching for heat sources you have detected in a thermal spotter and quick-and-easy acquisition and tracking of animals in cover. Thus, if you spot a fox that is too obscured by foliage to be immediately shootable, you can easily keep it in view as you squeak it in, or just wait for it to move into the open. This ability makes the Duo an absolute game-changer in summertime.

Which one?

Another key question is: “What’s the difference between the DXP55 and DXP50?” In simple terms, the 55’s daylight channel has a base magnification of 4X vs. 2X for the 50. As the base magnification of the thermal channel in both units is 2X, this means that the 50’s magnification, and its 12.4x9.3º field of view, are always in sync as you apply the digital zoom, and both top-out at 16X. By contrast, in the 55, the daylight channel always has twice the magnification of the thermal one and tops out at 32X. You can sync the 55’s magnification, but only at 4X, and only by first selecting the daylight camera as your primary channel before accessing the thermal channel via PiP. Except, that syncing the magnification really isn’t necessary, because you don’t use each channel the same way. Thus, target acquisition and tracking are best achieved in thermal at low magnification and with a wide FOV, whereas the daylight channel, with its higher magnification, shines at detailed quarry identification, effective obstacle detection (twig-avoidance!), and precise aiming.

Getting on target

A more important feature, with regard to synchronisation, is that each channel has to be zeroed independently. In each case, the process is simple. Begin by creating a profile (A-D) for the rifle, add the range to your zeroing target (e.g., 50m), and then use the zoom and freeze-frame functions to map the point of aim onto the point of impact. Three shots are usually enough. Once you have zeroed one channel, the Duo will prompt you to do the other. In reality, the collimation of the two channels is very good, but independent zeroing guarantees maximum precision whichever you aim with.

Verdict

I’ve gone on at length here about the dual-channel functionality of the Duo because that’s its unique feature, and I’m really excited by it. For information on all the many other features and functions of the Thermion range there’s not been room to describe here (e.g., ergonomic controls, dual batteries, intuitive menus, multiple reticle designs and colours, on-board recording, dual-band Wi-Fi connectivity, rugged and stylish design, superlative build quality, conveniently-sized 30mm main tube, solid distributor support, etc.), check out my previous reviews on Gunmart.net or visit UK distributor Thomas Jack’s website. I must confess that, prior to using the Duo, part of me was saying “OK. That’s clever. But what’s it actually good for?” Now, I simply want one. By night, it provides all the tried-and-tested benefits of Pulsar’s flagship Thermion 2 XP50 Pro, but by day, it augments the familiar capabilities of a day-scope to a genuinely game-changing degree. If you are primarily a night hunter, think seriously about getting the LRF for its new ballistic functionality, and if you spend any amount of time hunting in daylight, don’t think twice about getting the Duo. It’s amazing, and just £200 more than the standard XP50 Pro!