Most examples of night vision equipment base their operation on either thermal imaging or active illumination, both methods employ means to enhance and usually magnify the image. Thermal imaging detects emitted thermal or heat radiation, whose wavelength is well into the infrared region of the electromagnetic spectrum and therefore invisible to the human eye. The equipment produces a visible image based on the temperature difference between the background and the heat-emitting source, effectively outlining any warm-blooded creature against the cooler background. The military prefer this system, because it works in total darkness, rain, smoke and haze and it is not reliant on active illumination, which will give away the user’s position if the enemy is using night vision goggles.
The subject of this review, the Digisight LRF N850 is an active illumination type. It uses top quality components and produces an effective image for low light to no light shooting, observation and video recording. The review kit included useful optional extras, a battery pack, an infrared (IR) illuminator and a compact plug in video recorder. The scope and the additional IR illuminator are Yukon Advanced Optics Worldwide products under the Pulsar trademark, manufactured in Belarus and distributed by Queensland based Extravision Australia.
Active illumination night vision relies on image intensifying to produce a digital image from reflected low visible light radiation such as moon or star light when available, or the barely visible ‘near infrared’ radiation produced by the illumination unit when there is no visible light. In both cases, the radiation that ultimately forms the image is a reflection from the subject, rather than emitted radiation, as is the case in thermal imaging. The big advantage of this unit over earlier tube type image intensifiers is that it will work in full daylight without damage to its CCD sensor.. Extra light will not change the image, it will remain reliant on tones of grey for visual quality, similar to low contrast ‘black and white’ photography.
While bulky, its length is similar to a full size variable scope, and when in use on a rifle, the size does not pose a problem. The main section of the body is aluminium alloy with most attached fittings are plastic to keep weight down. A one-piece detachable aluminium mount, designed to fit Weaver bases comes with the scope. The unit has 4½ X optical and 2 X digital magnification, a 50mm objective lens and the reticle adjustment increments are 13mm at 100m or approximately ½MoA.
The Digisight LRF comes with a comprehensive set of built in options and adjustable features to maximise its effectiveness for a wide range of situations and individual preferences. Two quick and easy methods are available to zero the scope, (i.e. aligning the reticle centre with the rifle’s point of impact), and the scope can store respective zero data for three different rifles. Four different colour combinations are available for the reticle and the glowing dot in the centre, plus 13 different reticle choices including various sized dot and line marks for windage and elevation, a number of cross hair styles and illuminated elevation markings.
Magnification is essentially 4.5X (optical) this can be doubled by using the 2X digital zoom in 0.1X increments but resolution suffers. If the rifle is canted more than five degrees, the screen shows the shooter the direction and degree of incline, helping the shooter to eliminate cant. A supplied wireless remote control may be Velcro attached to the rifle’s fore end to enable basic scope and rangefinder controls, without removing either hand from the rifle. The integrated 400 metre range finder can operate in metres or yards, with or without calculating the true horizontal distance equivalent (THD), which allows the use of horizontal based trajectory data for inclined shots. A scan mode if selected will give updated distance readouts as the aiming mark is moved about. Rangefinder operation is quick and simple, the first press exchanges the reticle for the rangefinder indicator or aiming mark, a second press displays the distance to target.
The scope can be set to shut off automatically after 10 seconds if the scope is rotated more than 30° (laid on its side) or its axis is inclined more than 70° (stood upright). Flexible voltage external battery input, video output sockets, updatable software and a programmable button add to the utility of this versatile scope.
A shooter will find operating the Digisight quite different from a conventional scope. The main difference is the software switching of most of the settings via multifunction controls. This is inevitably slower than direct mechanical control. Slower setup is not a problem because most settings are a ‘one off’, or rarely need changing. Frequently used controls like brightness and focussing are instantly available. The contrast adjustment and power zoom, also often used, requires just one button push each to become the subject of the multifunction control knob. The wireless remote control was found to be particularly useful, it enabled three important controls; scope on/off, IR illuminator off/on/IR1/IR2, and the rangefinder to be operated from the shooting position.
Zeroing principle is the same as for conventional scopes but the point or area of impact needs to be visible on the Digisight screen. Hunters who want to zero in at a longer range may need a marker centred over the bullet hole, or preferably a group, to ensure easy visibility on the Digisight screen and thus enable adjustments. Because reticle adjustment is a slow indirect operation, most shooters will use the fixed zero and ‘hold off‘, or work out reticle elevation markers for longer than ‘point blank’ range shots. There is a choice of reticles for this purpose.
To test the ease and accuracy of zeroing, the Digisight was mounted on Jack’s Howa in .223 Remington, bore sighted at 50m and a single shot fired at this distance. The rifle was re-aimed, held still and crosshairs aligned with the bullet hole. As expected, this setting shot a high but ‘on paper’ group at 100m. For a final accurate zero, the re-aim and adjust (crosshairs to the group centre) process would be repeated to achieve a 100m zero.
Eye relief is sufficient for a well-held .308 Winchester but harder kickers, 67mm eye relief is not generous for heavy calibres. Users with glasses will need to press against the contoured flange of the light-shield for correct eye relief.
The scope performed well in daylight producing good resolution to enable Jack to shoot a 10.5mm group at 100m, as good as the rifle ever shot with its 4-16X power scope. At night, the scope showed its remarkable capacity to make use of very low light. On a clear moonless night it worked well without having to raise the 0 – 20 brightness setting above zero or use the illuminator. The photos show the typical brightness achieved but the resolution, when looking through the scope was much better than these hand held photos indicate. Looking at the built in illuminator from 20m, it appeared like a barely glowing dull-red spot, unlikely to cause alarm even at close range. (The similar N870 model has the invisible illuminator built in.)
The rangefinder worked well in ‘single shot’ and ‘scan’ mode, beyond the claimed 400m distance both day and night. At the same time, the illuminated dot reticle worked well even beyond 500m. However, this is a 4.5X scope designed for medium to bigger game at medium or shorter distances (say under 400m). Increasing the magnification via digital zoom inevitably degrades resolution and little if anything is gained.
The optional extras are practical and designed to operate with the Digisight. The Pulsar Battery Pack, retail price about $172 will supply 12V DC power to the Digisight for a claimed 9 to 20 hours of use.
The optional IR illuminator for $226, operates in the invisible infrared wavelength range and readily attaches to the top of the Digisight. It has its own power, two AA cells, and separate switch. A very compact Newton Sports Optics video recorder package for about $180 attaches neatly to the Digisight. It can record 80 minutes of video on the supplied 2 GB SD card and will accept a 4 GB card. Cables are supplied for output to Recorder, Video monitor and USB socket. The recorder is ideal for night observation but not recommended to be hard-mounted on the sight during shooting.
Pulsar’s Digisight is an impressive alternative scope suited to wildlife or stock observation and hunting at night without the disturbance of a spotlight. The scope will work equally well during the day and will suit hunters who want to start in the afternoon and continue to hunt into late evening, dusk and beyon. Battery life of the internal, four AA cells will easily cover a day’s hunting when only switched on to take a shot. For extended night use needing active illumination or continuous observation, the battery pack is the way to go. This equipment is capable of showing game a few hundreds of meters distant in the dark and also of measuring the effective shooting distance. The red or green illuminated dot assisted reticles make aiming easy and a high level of accuracy is possible if we stay within the distance limits of the 4.5X optical magnification.