Thermal range explained
How Far Can the Stellar 4.0 Identify a Fox, Pig or Deer?
The 2,600 m and 3,600 m figures on the Stellar 4.0 are detection ranges for something about the size of a person, and they mark the point where it first shows up as a few warm pixels. A fox stands about a fifth of that height. By our estimate from the lens and sensor specs, you'll recognise a fox at roughly 180–240 m on the Stellar 4.0 SQ50L and about 270–365 m on the Stellar 4.0 SX75L.
Pigs and deer, being bigger, hold their shape further out. The rest of this guide shows how we got those numbers and what they mean when you're scanning a paddock at night.
Where the 2,600 m figure comes from
Thermal makers quote detection range for a standard target, and HIKMICRO rates the SQ50L at 2,600 m and the SX75L at 3,600 m. Working backwards from the 12 µm sensor pixels and each lens, both figures line up with a target about 1.7 m tall covering roughly three pixels. That's enough to notice something warm, and nowhere near enough to say what it is.
The diagram below shows the same 2,600 m on the SQ50L's sensor. A person-sized target fills a short column of pixels; a fox fills about half of one.
Detect, recognise, identify
Range estimates for thermal scopes usually follow the Johnson criteria, a rule of thumb from military optics. About 2 pixels across a target's height lets you detect that something is there. Around 6 to 8 pixels lets you recognise what kind of animal it is, and about 12 lets you identify it with confidence, such as picking a fox from a cat, or a boar from a sow.
Each Stellar 4.0 pixel covers a fixed slice of the scene. By our estimate, that's about 2.4 cm at 100 m on the SQ50L and 1.6 cm on the SX75L, growing in step with distance. Divide an animal's height by that slice and you get the pixels it covers, which is how every distance in this guide was worked out. We cover the slice size itself in SQ50L vs SX75L: is the 1280 sensor worth the step up.
A fox on each sensor
Say you're driving a farm track after dark, scanning from the ute, and something warm sits near a fence line 300 m out. The diagram below shows what each scope puts on its sensor at 200, 300 and 500 m.
At 300 m, the fox covers about 5 pixels of height on the SQ50L. You'll see a warm shape, and its outline may suggest a fox, but you can't be sure yet. On the SX75L it covers about 7, which is enough to recognise it. The practical answer on the SQ50L is to range it, then close the distance or wait for the animal to move before deciding.
Foxes, pigs and deer at a glance
The table below runs the same sums for the animals most Australian thermal users shoot. Animal heights are approximate, measured at the shoulder.
| Animal (approx. height) | SQ50L: recognise | SQ50L: identify | SX75L: recognise | SX75L: identify |
|---|---|---|---|---|
| Rabbit (≈ 20 cm) | ≈ 105–140 m | ≈ 70 m | ≈ 155–210 m | ≈ 105 m |
| Fox (≈ 35 cm) | ≈ 180–240 m | ≈ 120 m | ≈ 270–365 m | ≈ 180 m |
| Wild dog (≈ 55 cm) | ≈ 285–380 m | ≈ 190 m | ≈ 430–575 m | ≈ 285 m |
| Pig (≈ 70 cm) | ≈ 365–485 m | ≈ 240 m | ≈ 545–730 m | ≈ 365 m |
| Fallow deer (≈ 90 cm) | ≈ 470–625 m | ≈ 310 m | ≈ 700–935 m | ≈ 470 m |
The bands below put the fox and pig figures on one scale, so you can see where each scope moves from naming an animal to just noticing it.
What pulls these distances in
These are clear-night figures. On a humid summer night, grass, dirt and animal sit close to the same temperature, and a distant target loses contrast before it runs out of pixels. Both models carry an under-12 mK NETD rating, which helps them hold contrast better than most hunting thermals, and we explain why in how NETD affects the thermal picture. Fog, rain and heat haze cut the distances further.
Body position matters too. A fox sitting side-on shows its full height and length; one facing you head-on shows far less. Treat every figure here as the best case, and let the 1,200 m rangefinder confirm the distance before you decide anything.
What this means for your choice
If most of your foxes and pigs are inside about 250 m, the SQ50L recognises them comfortably and identifies foxes out to about 120 m and pigs to about 240 m. If you regularly need to call animals at 300 m and beyond, the SX75L adds roughly 50% to every one of those distances. The trade-off is price and a shorter 7-hour battery rating against the SQ50L's 9.5 hours. Both models are covered in full in our HIKMICRO Stellar 4.0 review.
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Stellar 4.0 SQ50L Stellar 4.0 SX75LStellar 4.0 range FAQ
How far can the Stellar 4.0 identify a fox?
By our estimate from HIKMICRO's specs, the Stellar 4.0 SQ50L lets you identify a fox, telling it from a cat or a hare, out to about 120 m, and recognise one out to about 180–240 m. The SX75L stretches those to about 180 m and 270–365 m. Humid nights, rain and a head-on animal all pull these distances in.
How far can the Stellar 4.0 see a pig?
By our estimate, the Stellar 4.0 SQ50L lets you recognise a pig about 70 cm tall at roughly 365–485 m and identify it at about 240 m. The SX75L recognises one at about 545–730 m and identifies it at about 365 m. Detection, just noticing a warm shape, reaches well past 1,400 m on the SQ50L.
How far can the Stellar 4.0 recognise a fallow deer?
By our estimate, a fallow deer about 90 cm at the shoulder is recognisable at roughly 470–625 m on the Stellar 4.0 SQ50L and 700–935 m on the SX75L. Identifying it with confidence, for example a buck from a doe, needs you inside about 310 m on the SQ50L or 470 m on the SX75L, and usually closer in timber.
How far can the Stellar 4.0 see a rabbit?
Rabbits are small, so the distances shrink. By our estimate, a rabbit about 20 cm tall is recognisable at roughly 105–140 m on the Stellar 4.0 SQ50L and 155–210 m on the SX75L, and you'll notice one as a warm dot out to about 420 m and 625 m. For rabbit work, either scope covers normal spotlighting distances easily.
How far can the Stellar 4.0 see a wild dog?
By our estimate, a wild dog about 55 cm at the shoulder is recognisable at roughly 285–380 m on the Stellar 4.0 SQ50L and 430–575 m on the SX75L. Telling a wild dog from a large fox or a farm dog takes more detail, so plan on identifying it inside about 190 m on the SQ50L or 285 m on the SX75L.
What is the difference between detect, recognise and identify?
They are three levels of detail from the Johnson criteria. Detect means you can see something warm is there, at about 2 pixels across its height. Recognise means you can tell what kind of animal it is, at about 6–8 pixels. Identify means you can be confident, such as a fox versus a cat, at about 12 pixels.
Why is the Stellar 4.0's detection range so far?
The Stellar 4.0's rated detection ranges, 2,600 m for the SQ50L and 3,600 m for the SX75L, describe when a person-sized target first appears as a few warm pixels. By our estimate, that's a target about 1.7 m tall covering roughly three pixels. Smaller animals appear much closer, and recognising them needs several times more pixels.
Does zooming in increase how far I can identify an animal?
No. Zooming in on the Stellar 4.0 enlarges the picture on the display, but the number of sensor pixels covering the animal stays the same, so the detail you can resolve doesn't change. Zoom helps you look closer at an animal you've already found. To see more detail, you need to get closer or use the SX75L's finer pixels.
Do fog and rain reduce thermal scope range?
Yes. Fog, rain and heavy mist absorb and scatter infrared energy, so a distant animal loses contrast and fades sooner. Humid nights do the same more subtly, because the animal and its background sit closer in temperature. The Stellar 4.0's under-12 mK NETD helps it hold contrast, but expect shorter distances than our clear-night estimates in poor weather.
All distances in this guide are our estimates, calculated from HIKMICRO's published Stellar 4.0 sensor and lens specifications using the Johnson criteria.