Eyeskey Night Vision GL521 monocular review

A night vision device (NVD) is an electro-optical device that allows observation in low-light conditions. The main application of night vision devices is, of course, military, but NVDs are also used for hunting, for observing wild animals, for protecting territory, in astronomy, physics, medicine, etc. I got a Night Vision GL521 night vision device from Eyeskey for review. This NVD is based on an image intensifier tube (ITT), which amplifies light by several tens of thousands of times. That is, it is not a thermal imager, but actually an “amplifier” of the light flux.

Eyeskey Night Vision GL521
Eyeskey Night Vision GL521

In absolute darkness, such a device will not show anything, but even a weak source of illumination (sky, stars, Moon) is enough to show what is not visible to the eye. Eyeskey GL521 is a passive night vision device – it does not have infrared illumination, as in security cameras and inexpensive NVDs based on CMOS matrices, but it perfectly sees the near infrared range (up to 1000 nanometers for sure).

In turn, the image intensifiers are divided into several generations: I, I+, II, II+, Super GenII+, III.
In inexpensive civilian NVDs, the first generation image intensifiers are usually used (light gain up to 2000 times).
In generation II, an additional electron amplifier is used – a microchannel plate detector(MPD), due to which the light gain is significantly higher than that of the first generation.

In turn, the SuperGenII+ generation is several times more sensitive (light gain up to 40,000) than II+ (light gain up to 30,000). At the same time, the compact size of the second-generation converters allows for a significant reduction in the size of night vision devices. The Eyeskey Night Vision GL521 device under review is declared to have a “Gen. 2+ LLL image intensifier”.

Devices with III-generation image intensifier tubes are even more sensitive (especially in the infrared range) than II+ and SuperGenII+, but are rarely found on the open market due to their high cost.

Generation II+ image intensifier circuit
Generation II+ image intensifier circuit

Specifications declared by the manufacturer:

The device is supplied in a small cardboard box.
Inside the box:
-night vision device
-magnetic charger adapter
-USB charging cable with Type-C connector on one end and USB-A on the other
-charger with USB-A connector
-lanyard
-instructions
-microfiber cloth.

Коробка
Box
Содержимое коробки
In the box
Комплектация
In the box

The device has a built-in battery, user replacement is not provided, capacity is not specified. The complete charger has an output voltage and current of 5V 1A, but the plug format is Chinese – either an adapter or a different charger is required. Perhaps an external battery (powerbank) can be used for charging.

Магнитный адаптер зарядного устройства установлен
Magnetic charger adapter installed

The form factor of the night vision device is a monocular. The device body is completely metal, the lens and eyepiece are covered with identical metal caps with a small hole in the center, the thread on the caps is M40. The length of the monocular is 111.2 mm (with caps), the diameter is 43.83 mm. There are several movable rings with notches on the body – one for focusing, the other for turning the device on and off with the inscription ON-OFF. Also in the front part there is a magnetic socket for the charger.

Общий вид
General view
Общий вид со стороны зарядного порта
General view from the charging port side
Сравнительные размеры
Comparative sizes

In the front part there is a 22 mm diameter lens with a lilac coating, the front lens is convex, there is an inscription 00143-22/GL521/YNOE.

Вид спереди
Front view
Объектив
Lens

The eyepiece lens is 26.9 mm in diameter, convex, with a lilac coating. The measured field of view of the eyepiece is 40.7 degrees. There is a double lanyard hole in the back of the housing.

Вид сзади
Rear view
Окуляр
Eyepiece

ATTENTION! TO AVOID DAMAGE, USING THE NIGHT VISION DEVICE BASED ON THE IMAGE INTENSIFIER TUBE IN BRIGHT LIGHT WITHOUT THE PROTECTIVE COVER WITH A HOLE ON THE LENS IS STRICTLY PROHIBITED! DO NOT POINT THE DEVICE AT SOURCES OF BRIGHT LIGHT – FLASHLIGHTS, CAR HEADLIGHTS, THE MOON, THE SUN, AS WELL AS SOURCES OF INFRARED RADIATION – SECURITY CAMERAS, SCREENS AND CAMERAS OF SMARTPHONES, ETC.

Before using, the device must be fully charged. To check the operation in bright light, unscrew the cap on the eyepiece (near the lanyard hole, do not mix it up!). To turn on the device, turn the power ring slightly to the ON position. Look into the eyepiece. The image in it will be green – this is normal. If the image is blurry, adjust the focus by rotating the front ribbed ring. If you have poor eyesight (nearsightedness, farsightedness), use glasses.

Before using the device at night or in the twilight, turn off all bright light sources (flashlights, headlights) and go to a dark place without lighting. Unscrew both covers from the device. Turn on the device by turning the ring, look into the eyepiece, focus if necessary. The visibility of objects should be better than with the eye – about the same as during the day, but everything is green.

The magnification of the device is 1x – that is, the magnification is the same as seen by the eye, in fact, there is no approximation. This has a number of advantages, as the field of view is much wider, it is easier to correlate scales and distances. However, due to the lack of zoom, detecting distant ground objects can be difficult.

I was impressed by the work of the Eyeskey Night Vision GL521 night vision device already during the first test at night in the yard. Where the eye sees darkness, the device shows almost as if it were daytime. The sharpness across the field is good, with a slight flattening of the image towards the edges. Small dark spots are visible in the field of view.

Тест во дворе
Backyard test

But for me, as an astronomer, it was most interesting to test the device in the night sky, in nebulae and clusters, because the form factor of the device itself, as well as 1x magnification, hint – look at the stars! A multitude of stars and flying satellites immediately appeared in the sky. Some stars seemed especially bright, although in the sky they were dim to the naked eye – perhaps these stars emit mostly in the red and near infrared ranges. Even being in the center of an illuminated city, I immediately saw the Andromeda Galaxy, a double star cluster in Perseus. Obviously, such a device can be extremely useful for observing meteors. And when using a narrow-band hydrogen filter H-alpha 12 nm 1.25″, installed IN FRONT of the primary lens, I clearly saw the outlines of the “North America” ​​and “California” nebulae WITHOUT A TELESCOPE. I also noticed a nebula around the star Sadr in the center of Cygnus. When using the filter, the image became noticeably noisier – most likely, the device uses automatic gain control (AGC). Unfortunately, the smartphone camera does not accurately convey what is seen in the NVG – with the eye the picture is much cleaner and more detailed. In general, a black and white image intensifier tube would be better suited for astronomical observations, rather than a green one (yes, they exist), since through a telescope most nebulae and galaxies are visible in shades of gray.

Созвездие Лиры
Constellation Lyra
Созвездие Лебедя с водородным светофильтром H-alpha 12 нм.
The constellation Cygnus with a 12 nm H-alpha hydrogen filter.

I also tried observing through the NVD directly through the telescope eyepiece – for the test I used a refractor telescope with an aperture of 102 mm and a focal length of 660 mm. The eyepiece has a focal length of 32 mm. The exit pupil was about 5 mm, but most likely, for a brighter picture it is desirable that it be comparable to the size of the NVD lens. In the city overexposed sky with a 12 nm H-alpha filter, the image of nebulae such as “Veil” or M27 “Dumbbell” was significantly better than without the NVD and without a filter. “North America” ​​was visible much worse than without a telescope – perhaps due to the small exit pupil with a specific eyepiece. Nevertheless, the effect of using the NVD is definitely there. I also tried observing through a two-band Optolong L-eNhance filter (H-alpha, OIII + H-beta) – the background became noticeably brighter, the visibility of nebulae worsened compared to H-alpha 12 nm. For better matching with the eyepiece, it is advisable to make an adapter. It may also be necessary to purchase an eyepiece with a longer focal length and (or) a high-aperture telescope to provide a large exit pupil (about 22 mm).

The device perfectly sees infrared radiation from the remote control, from the smartphone proximity sensor, from the laser infrared illumination unit of the smartphone cameras. You should not point the night vision device at them. The short-term beam from the laser rangefinder (wavelength about 1000 nm), which is not visible to the naked eye, is also perfectly displayed on distant objects.

Pros:
+ compact body, looks like a regular monocular.
+ bright image even in low light
+ good image quality – both on axis and across the field

Cons:

– the on/off ring is tactilely similar to the focus ring, it would be better to make it more ribbed, the grip with the finger is poor.
– the case is quite slippery.
– there is no battery level indicator. It is advisable to fully charge the device before long-term use.

SUMMARY

I liked the effect of the device. I think that the Eyeskey Night Vision GL521 night vision device has a certain potential for astronomy enthusiasts. Of course, this NVD can also be useful in other areas where low-light observation is required. I recommend it!

2 thoughts on “Eyeskey Night Vision GL521 monocular review”

  1. Сергей

    Ф сколько стоит этот ПНВ? И где можно его приобрести.
    Спасибо.

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