Pulsar Axion A2 XG35 thermal imager
WHEN it comes to choosing and using conventional optical equipment, a high lightgathering capacity has long been considered a fundamental prerequisite – particularly towards the end of the day, when low light conditions prevail. But after the sun has set, crossing the line to the ‘dark side’ requires an altogether different approach to observation.
Enter, thermal imaging.
The technology behind the devices that deliver this has been improving over the years
– so much so that they are increasingly being used for nature observation, not only in the hours of darkness but also during the daytime.
Having previously reviewed products which deliver images in the dark, it’s useful at this stage to differentiate between ‘thermal imaging’ and ‘night vision’. Models in the latter category have been around for many years and they detect small amounts of visible light and amplify it so an image can be seen. Many have built-in, infrared illuminators to allow usage in ambient light or in total darkness. Thermal imaging, however, detects ‘heat’ from bodies (human and animal) relative to the surrounding habitat, using near-infrared or ultraviolet radiation, as opposed to simply drawing in ‘light’.
Such devices have been popular with the hunting fraternity for some years but they have been slow to catch on in the world of birding. Prominent among pioneers of their use in the UK, the West Midlands Ringing Group has been using them since 2016, locating elusive birds for ringing by night and day, surveying roosting birds and checking nestbox occupancy.
They have been instrumental in improving the catch rate for ringing surveys of birds such as Eurasian Skylark, Eurasian Woodcock and Common and
Jack Snipe, as well as increasing efficiency in surveys, reducing disturbance of birds and delivering an improvement in the accuracy of counts for birds of conservation concern.
Launched in June 2022, the Axion 2 XG35 is the topperforming compact thermal monocular in the range manufactured by Pulsar and I was pleased to be able to trial one in both the shortening days and lengthening nights of November.
A rubber-armoured magnesium alloy body houses a powerful 640x480 microbolometer (thermal imaging sensor), which is capable of detecting warm-bodied animals and birds at distances up to 1,750 m. Four control buttons are positioned in a straight line along the roof of the body and there’s a wrist strap located on the right-hand side. This set-up simply means it is possible to slip your hand through the strap, position your thumb on the underside of the body and use four fingers to operate the top line controls. It took some practice, though.
The rechargeable Lithium-ion battery pack runs the length of the body, every part of which is sealed against moisture and the whole device is IPX7-rated, which means it can be submerged in water, to a depth of 1 m, for up to 30 minutes.
I found the XG35 very easy to operate. After switching the unit on using the control button nearest the objective, the eyepiece can be rotated to bring into focus the symbols on the screen. This effectively performs the same function as the dioptre in a conventional binocular. Once focused, it’s simply a matter of choosing menu settings, which can be selected using the up/ down buttons on top of the device. Subsequently rotating the objective lens focusing ring will then bring into focus the object