Thermal limitations?
- Thread starter Poola
- Start date
I have never had a problem with thermal and midges: its an intriguing (and likely near-agonising!) problem, but I suspect very much second order.
But attenuation from rain and drizzle is, in my experience, THE key challenge for thermal. This is not a problem of different manufacturers and/or products, but the essence of the technology. Water (be it mist, drizzle, or heavy rain) is very cooling, and therefore can absorb much of what is often only a very small difference in the heat signature of the animal we are looking for.
At its worst, I have experienced poor weather causing a perhaps 75% reduction in thermal detection range compared to “normal” conditions (assessed when scanning at known range from a known spot). It is seldom as bad as this, but you should, in my view, not expect detection performance NOT to vary, sometimes significantly.
But attenuation from rain and drizzle is, in my experience, THE key challenge for thermal. This is not a problem of different manufacturers and/or products, but the essence of the technology. Water (be it mist, drizzle, or heavy rain) is very cooling, and therefore can absorb much of what is often only a very small difference in the heat signature of the animal we are looking for.
At its worst, I have experienced poor weather causing a perhaps 75% reduction in thermal detection range compared to “normal” conditions (assessed when scanning at known range from a known spot). It is seldom as bad as this, but you should, in my view, not expect detection performance NOT to vary, sometimes significantly.
Midges shouldn't be an issue from a thermal perspective.
Image. Bear in mind that you're looking at a temperature map, not a sight picture. The map is built on the basis of temperature difference, so with rain and fog, both can have the effect of normalising the temperature, so reducing the effectiveness of the unit, as has been said above. If two things are the same temperature, you will not be able to distinguish them apart. In the worst conditions an animal can look like it's floating in a soup, so you do need to know your ground - but you can mitigate this with changing settings to an extent. In fog - well I've seen things in thermal that I then couldn't shoot...... but distance can be impacted, especially where very thick.
On 38 v 50 - If you are doing any scanning in woodlines and within 100m - go for the 38. You'll find the FoV very frustrating otherwise. I really wouldn't worry about the detection range.
HTH
Image. Bear in mind that you're looking at a temperature map, not a sight picture. The map is built on the basis of temperature difference, so with rain and fog, both can have the effect of normalising the temperature, so reducing the effectiveness of the unit, as has been said above. If two things are the same temperature, you will not be able to distinguish them apart. In the worst conditions an animal can look like it's floating in a soup, so you do need to know your ground - but you can mitigate this with changing settings to an extent. In fog - well I've seen things in thermal that I then couldn't shoot...... but distance can be impacted, especially where very thick.
On 38 v 50 - If you are doing any scanning in woodlines and within 100m - go for the 38. You'll find the FoV very frustrating otherwise. I really wouldn't worry about the detection range.
HTH
mn87
Active Member
I was out on Tuesday evening here, It was warm, wet, damp, drizzle, rain (i.e. very poor conditions for thermal) and although range was reduced, it still picked up far more than I would ever have seen without it. Even if I couldn't tell it was a deer (at distance) I certainly knew there was an animal there and could confirm with the binos (As I knew where to look), but often the thermal is seeing clearer (even in these conditions) than the bins and im using Swaro 10 x 42.
Certainly as Eric said above, I have seen things in the thermal which you would not be able to shoot or even pick up with binos
I have the XM30s but have used the XQ38 a good number of times on ground similar to what you describe (Large replant and valleys). Even in poor conditions we can see deer regularly out to 800 - 1000m, and certainly a heat source out that far in the worst conditions, likelyhood is its a deer if you know the ground and what else could possibly be there.
I would suggest that the days where thermal conditions are that poor that the unit is not useful would be fairly few.
Midges - never a problem as mentioned above.
Certainly as Eric said above, I have seen things in the thermal which you would not be able to shoot or even pick up with binos
I have the XM30s but have used the XQ38 a good number of times on ground similar to what you describe (Large replant and valleys). Even in poor conditions we can see deer regularly out to 800 - 1000m, and certainly a heat source out that far in the worst conditions, likelyhood is its a deer if you know the ground and what else could possibly be there.
I would suggest that the days where thermal conditions are that poor that the unit is not useful would be fairly few.
Midges - never a problem as mentioned above.
Very much agree with this, I have an XQ50 but only because I got it at a very good price, would likely have one for the 38 or if I had the money the XP50F as the 2.5x minimum mag is workable for shorter ranges. The 4.1 times of the XQ50 is hard work closer in and I have taken to holding the unit diagonally to give the widest FOV!! I came over to the helion from a Flir Ls-XR which although older and not as sharp as the helion had a base mag of 1x and was awesome for searching close in.
Further really helpful advice, and exactly what I was hoping for - thanks all. It’s certainly helped consolidate the decision to buy one... Just wavering now perhaps towards to XQ38f: I wouldn’t be doing much generally at less than 100m, but that’s not to say never - so will give further thought what has been said on fov...
I really appreciate your time in responding!
I really appreciate your time in responding!
Happy stalker
Well-Known Member
Cold clear winter nights are superb for thermals my own Helion XP38 over restocks very little goes undetected 
You say you won’t be doing much below 100, one of the best things with thermal is it is invaluable for finding a deer that runs into cover, maybe at last light, thermal with low mag is absolutely brilliant for this.
The 4.1x of the xq50f means it is severely lacking in this department, in fact it’s rubbish!
Another possible consideration when deciding between 38 or 50 is what optic system you will be using to actually take the shot?
I use a Helion XM50 thermal spotter (4:1 lowest mag) but then use IR (Photon XT with doubler) for confirmation & shot which is 10.5x mag. For me any perceived ‘close in’ advantages of 2.5 mag possibly become academic given my choice of IR (although playing devils advocate you could also argue that the more reference points that you have from the thermal the easier it is to acquire the quarry through the IR’s tighter FOV)? No right or wrongs really...... just whatever you prefer?
The prime limitation that has already been mentioned however is that thermals rely on a good ‘thermal gradient’ to work I.e. hot beast against a cold winter background =
; hot beast against hot background e.g.sun baked rocky or ploughed ground = 
. Anything in between the lens & target that interferes with heat detection e.g.mist, rain, or even heat haze effectively acts as a ‘screen’ and reduces clarity in proportion to the density’ of this ‘screen’.
Hope this helps but either way one thing is for sure - once you’ve used thermal you’ll never go back. Absolute game changer
I use a Helion XM50 thermal spotter (4:1 lowest mag) but then use IR (Photon XT with doubler) for confirmation & shot which is 10.5x mag. For me any perceived ‘close in’ advantages of 2.5 mag possibly become academic given my choice of IR (although playing devils advocate you could also argue that the more reference points that you have from the thermal the easier it is to acquire the quarry through the IR’s tighter FOV)? No right or wrongs really...... just whatever you prefer?
The prime limitation that has already been mentioned however is that thermals rely on a good ‘thermal gradient’ to work I.e. hot beast against a cold winter background =
; hot beast against hot background e.g.sun baked rocky or ploughed ground = . Anything in between the lens & target that interferes with heat detection e.g.mist, rain, or even heat haze effectively acts as a ‘screen’ and reduces clarity in proportion to the density’ of this ‘screen’.Hope this helps but either way one thing is for sure - once you’ve used thermal you’ll never go back. Absolute game changer
Freeforester
Well-Known Member
Moist conditions make for an equal surface temperature in most things, making the contrast between live and inanimate o jests less clear, and inanimate objects and the background very indistinct.
With experience and use your still going to be able to see, just not so well, same with hot and hot surroundings, it's still possible, just not ideal.
With experience and use your still going to be able to see, just not so well, same with hot and hot surroundings, it's still possible, just not ideal.
Another possible consideration when deciding between 38 or 50 is what optic system you will be using to actually take the shot?
I use a Helion XM50 thermal spotter (4:1 lowest mag) but then use IR (Photon XT with doubler) for confirmation & shot which is 10.5x mag. For me any perceived ‘close in’ advantages of 2.5 mag possibly become academic given my choice of IR (although playing devils advocate you could also argue that the more reference points that you have from the thermal the easier it is to acquire the quarry through the IR’s tighter FOV)? No right or wrongs really...... just whatever you prefer?
The prime limitation that has already been mentioned however is that thermals rely on a good ‘thermal gradient’ to work I.e. hot beast against a cold winter background =
Hope this helps but either way one thing is for sure - once you’ve used thermal you’ll never go back. Absolute game changer
Possibly doesn’t apply for stalking use.
Must admit for NV work I like variable magnification, 3/4 x for picking up the target and zoom in 10-20 depending on scope and range for the shot.
Happy stalker
Well-Known Member
What I would say about thermals is they are definitely a game changer for crop protection out on clear winter nights doing what we have to do to get the job done.
I use my binoculars during daytime so I don’t lose the knack of spotting beasts which has been gained over many years sadly there are some folk out there all they know is thermal and they struggle to spot beasts using binoculars
I use my binoculars during daytime so I don’t lose the knack of spotting beasts which has been gained over many years sadly there are some folk out there all they know is thermal and they struggle to spot beasts using binoculars
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