NHBS Guide to Night Vision and Thermal Optics

There are many scenarios where our attempts to observe and survey certain species are hampered by our limited sensory systems. Many animals are difficult to detect because they utilise cryptic colouration or disruptive patterns, or they have evolved ingenious behaviours to conceal themselves within their environment. In other cases, environmental conditions such as low light levels or fog, can reduce visibility and disguise even some of our most obvious resident species.

Ecologists, researchers and amateur wildlife enthusiasts have overcome these sensory limitations by using thermal imaging and night vision optics. This article will cover how these different technologies function, highlight their key specifications and give recommendations for those looking to purchase one of these devices.

© Dûrzan cîrano

Thermal Imaging

Thermal imaging works by using an electronic detector element to convert the infrared light (heat) emitted by objects in the environment into a visible pattern of colours that vary depending on the temperature of the object. Thermal imaging devices (TIDs) are becoming increasingly common in ecological surveys because, unlike night vision devices, they can produce an image in daylight or complete darkness, even through fog.

When choosing a TID there are a few key technical specifications that you should consider for your project:

  • Resolution – The clarity of the images/videos is determined by the number of heat sampling points. The higher the resolution, the easier it is to spot small animals at a distance.
  • Refresh Rate – Determines how often the screen is updated with a new image. A refresh rate of 30Hz or more is recommended for fast-moving animals such as birds and bats.
  • Zoom – This is particularly useful for larger species identification and counting your target more accurately.
  • Field of View (FOV) – The horizontal and vertical angle of view that you can see through the thermal imaging device. A wider field of view is useful when detecting small animals.
  • Maximum Detection Range – Gives an indication of how far the device will be able to detect a human-sized object effectively.
Pulsar Axion XM38

This thermal monocular has a compact, ergonomic design and features all the excellent capabilities of Pulsar’s more advanced thermal imaging devices.

  • Refresh rate: 50Hz
  • Sensor resolution: 320 x 240p
  • Digital zoom: 2x, 4x
  • Field of view: 5.8° horizontal
  • Max Detection Range: 1700m
  • Video Recording: Yes
  • Streaming capabilities: Yes
  • Price: £2,059.99



See the full range of Pulsar Axion models

Pulsar Helion XP50

A powerful thermal imaging monocular with an impressive resolution and detection range, as well as full remote control through the Stream Vision app on a smartphone or tablet.

  • Refresh rate: 50Hz
  • Sensor resolution: 640 x 480p
  • Digital zoom: 2x, 4x, 8x
  • Field of view: 12.4°
  • Max Detection Range: 1800m
  • Video Recording: Yes
  • Streaming capabilities: Yes
  • Price: £3,949.99

See the full range of Pulsar Helion XP & XQ models

Seek Thermal CompactPRO FF

Designed to be used with a smartphone or tablet these compact thermal detectors can be easily transported and are excellent for impromptu use.

  • Refresh rate: 15Hz
  • Sensor resolution: 320 x 240p
  • Digital zoom: 2x
  • Field of view: 32°
  • Max Detection Range: 550m
  • Video Recording: Yes
  • Streaming capabilities: No
  • Price: £479.95

See the full range of Seek Compact models

Seek Shot

Designed to be used quickly and conveniently, these pocket-sized devices are excellent for obtaining thermal images of species such as bats when they are roosting in crevices and cavities. It is also available in a Pro version which has a greater sensor resolution and field of view.

  • Refresh rate: <9Hz
  • Sensor resolution: 206 x 156p
  • Field of view: 36° horizontal
  • Max Detection Range: 300m
  • Video Recording: Yes
  • Streaming capabilities: Yes
  • Price: £579.95

 

Night Vision

Night vision technology operates either by using an image-intensifier tube (analogue) or an electronic sensor (digital) to amplify the small amount of light present in dark environments to generate a bright image. They typically produce a monochromatic green or greyscale image, however some newer technologies are now able to capture colour images in low light conditions.

There are a few specifications that you should consider when choosing an night vision device (NVD):

  • Viewing Range – The distance to which you can see and distinguish objects using the device can be crucial for certain projects. A low-end NVD will typically have a viewing range of around 200m, while more high-end models can achieve viewing ranges of up to 500m.
  • Analogue Night Vision – These scopes are grouped into generations. Gen 1 scopes are the most economic but have a limited range (approximately 75m), lower resolution and limited field of view. Gen 2 and 2+ scopes offer performance improvements such as longer range, better image resolution and greater field of view.
  • Digital Night Vision – Digital devices typically produce higher quality images than Generation 1 scopes, often have a video output or SD card allowing video capture.
  • IR illumination – Most night vision devices have a built in IR illuminator to increase the brightness of the images it takes, however purchasing an additional IR illuminator may be necessary when working in extreme darkness.
SiOnyx Aurora

New for 2019, this innovative night vision monocular utilises SiOnyx’s Ultra Low-Light Sesnor Technology to record colour footage not only during the day but also in both low-light and night-time conditions. It also features a wifi module to stream or transfer photos and videos, as well as a GPS module to automatically geotag and timestamp recordings.

  • Digital: Ultra Low-Light CMOS sensor
  • Digital Zoom: 1-3x
  • Field of view: 42°
  • Display colour: Colour, phosphor green, monochrome
  • Video Recording: Yes
  • Streaming capabilities: Yes
  • Price: £799.99
Bushnell Equinox Z2

An impressive digital night vision monocular with a high sensor resolution and viewing range of up to 230m. It can take HD video recordings which can be streamed over Wifi using the dedicated Equinox Z2 App.

  • Digital: CMOS sensorDigital Zoom: 1-3x
  • Field of view: 105m @ 1000m
  • Display colour: Colour (in daylight), greyscale
  • Video Recording: Yes
  • Streaming capabilities: Yes
  • Price: £421.00



See the full range of Bushnell Equinox Z2 models

Yukon NVMT Spartan

An excellent gen 1 monocular that has been designed for ease of use in complete darkness. It is operated using only three buttons and features a lightweight and compact body-shell to protect against any damage.

  • Analogue: Generation 1
  • Lens diameter: 50mm
  • Magnification: 4x
  • Field of view: 15°
  • Display colour: Phosphor green
  • Video Recording: No
  • Streaming capabilities: No
  • Price: £235.00


MORE INFORMATION

To learn more about some of these products or to browse our full range of night vision and thermal imaging optics visit our online store at NHBS.com.

If you would like some more advice on choosing a thermal imaging or night vision device contact us via email at customer.services@nhbs.com or phone on 01803 865913.

Collecting visual evidence of bats at roost entrances

Aim
Recording bats and their behaviour around roost entrances can be extremely useful for a number of reasons: as evidence to present to a client, to demonstrate or test for a change in behaviour during or after mitigation, and as a back-up system to record the presence of the quieter bats like the brown long-eared. We tested two night vision systems at a lesser horseshoe maternity roost.

Yukon Stringer 5 x 50 Night Vision MonocularPulsar Quantum S Series Thermal Imaging Scope

Methods

We set up two very different night vision video recorders on tripods near the entrance of a large lesser horseshoe roost near Totnes, Devon. The first was the Yukon Stringer 5 x 50 Night Vision Monocular, a very reasonably priced Generation One night vision device with a built-in video recorder. The second was the Pulsar Quantum HD38S Thermal Imaging Scope, a thermal imaging camera with a 30 Hz refresh rate coupled with a Yukon MPR Mobile Player / Recorder. Both were used to film bats as they emerged from the roost entrance and as they flew around the garage within which the roost entrance is sited.

Results
The two videos below demonstrate close-up and distance footage from both the Yukon Stringer and the Pulsar Quantum:

Video: Surveying a bat maternity roost - Close upVideo: Surveying a bat maternity roost - At a distance

Discussion

Image Quality: The Pulsar Quantum produced some very high quality video that was clear and easy to interpret. The results from the Yukon Stringer are slightly less clear but are still of sufficiently high quality for most purposes.

Usability: The Yukon Stringer does have a much narrower depth of field and due to the fixed zoom it proved very hard to get any decent footage of the bats flying around within the garage space.

Battery Life: The only drawback was the short battery life of both the Quantum and the Yukon MPR Mobile Recorder. To get round this we used the EPS5 External Battery on the Pulsar Quantum and changed the batteries of the Yukon MPR regularly – not the ideal solution but the cheapest way we know of to get some really impressive thermal imaging video.

Night Vision Scopes at NHBS

Night vision scopes work by collecting available light, normally from the moon and stars, and amplifying this to generate a meaningful image. The main component of any scope is the Image Intensifier, a vacuum tube that differs in design depending on the generation of scope (more info on generations later!). The image intensifier collects particles of light (photons) and focuses them onto a photocathode. The photocathode absorbs these photons and converts them to electrons, which are subsequently amplified and projected onto a green phosphor screen at the rear of the tube. To do this the photocathode needs a power supply, normally from commercially available batteries.

When the electrons hit the phosphor screen, the screen emits visible green light that the user can see. Therefore, you do not look through a night vision scope, but rather look at an amplified electronic image on a phosphor screen. As the phosphor screen emits light in exactly the same pattern and intensity as the light collected by the objective lens, the screen image corresponds to the actual scene in front of the scope. The phosphor screen is coloured green because the human eye can differentiate more shades of green than any other phosphor colour.

There is a bewildering array of night vision scopes available for amateur, commercial and military purposes. NHBS has selected a range of scopes and accessories that match the needs of amateur and commercial users so we hope there is no chance you are going to get shot at whilst using them! All our scopes have been tried and tested by wildlife and land management professionals and so provide versatile and durable solutions to seeing at night. However, even amongst our range there are subtle differences that make some scopes more suitable than others for certain uses. Below is a list of criteria to consider when making your choice. If you are still unsure, then please contact us as we would be happy to provide further advice.

For more on this blog, see the NHBS Quick Guide: Night Vision Scopes