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Night Vision Thermal imaging - 2 Questions

S

stag

Private
Full Member
Minuteman
Nov 1, 2008
4
0
#1
Thermal imaging - 2 Questions



1/ I've been told that thermal imaging works reasonably well in misty conditions, the lens on my image intensifier form a moisture layer on the front lens which degrades the image, does this have a negative effect with thermal imagers.

2/ I'm intrigued to know how you zero thermal weapon sights, my normal zero distance for a image intensifier would be 200yds does anyone have any "hot" tips!
 
#2
stag,

Yes thermal imaging (depending on the unit of course) works very will in misty and foggy conditions. Your second question is difficult to answer being model agnostic. Perhaps you could tell us what model you're interested in? I zero at 100 yards for any unit that is 640 and up as it's pretty much a standard. (and I zeroed my old 240 stuff at 50 yards.)
 
#3
I'd shoot at 100yrds to zero but just sight it in 1 1/2" high or whatever you need for 200yrds. Try sticking a piece of chewed bubble gum on the target. Anything with some heat will shine good for your aiming point!
 
#4
Targets... Look up exothermic chemical reactions. You want the safer ones, think pocket hand warmers, back warmers. I'm not a chemist, so keep that in mind, I just know that's cheaper and more efficient for us than using the real heated targets. But you CAN modify a toaster or other nichrome wire heating element to electrically heat an AR500 target from behind using a car battery and a simple circuit. Back heating pads work too but take longer to work and insulation on the back to cover it is ideal.

They do in fog and rain and zero light what the NODs can't. Here in WA, you NEED the high end hand select 3rd gen. NV shit just to get by during rainy season. Even then the best is still kinda fuzzy. Thermal is SO much better then, and it's hard as hell to hide from it under most conditions.
 
#6
Buy a couple chem sticks. Put them behind the target with a whole cut the size of a quarter, site in at 50 yards and you will knock em stiff easily out to 200. Of courese that depends on caliber and your shooting ability
 
#8
We went out hunting in the middle of a tropical storm at night last year, torrential rain and winds howling up to 75 mph, it was crazy but allot of fun too.

NV was simply next to worthless in the completely black dark night with teaming rain, thermal was the only thing that worked.

We managed to take out a number of hogs in what was otherwise completely inhospitable conditions when even a flashlight was next to worthless in the swamps....thanks to thermal.

Dom%20Dragging%20Hog.jpg


Sow%20&%20Piglets3.jpg
 
#13
Bump.. Didn't want to start a new topic and it's on topic.

I've been thinking of getting a thermal viewer but I'm a little unsure of how effective it would be I just went outside at 2030 and measured the ground temp it's 32*c (89*f) am I correct in thinking that I will not be able to see most animals because of the ground temp ?

I looked up the average temp of a pig and its 38.7-40 °C (101.6-104° F) is that enough of a temp difference to detect pigs at night ?
Or would I be better off sticking with NV ?
.
 
#15
There are times when the sun is beating down on everything in the desert when soft targets are less well defined, but there are not many circumstances where Thermal does not surpass I2 for detection. But, Get in some of those conditions, or a low resolution unit and some distance between you and your target and you'll find yourself wondering..."dog or coyote? Calf or hog?
I feel like you are missing out if you don't have both.
 
#16
Stag I will attempt to give you a crash course on thermal optics and hopefully you'll walk away with more knowledge! so here goes..

1. First thing ill go over is thermal infrared theory. Thermals take in light energy radiated from a scene and senses differences in apparent temperatures of the area and in turn converts the differences to a visible image. Three factors play for thermal optics. They are exposure (radiation-from source, conduction-earths core & man made objects, convection-wind:hot or cold), absorbtion (how well it absorbs energy, reflects energy and amount of exposure time) and emissivity- the rate of an object releasing absorbed energy.
*absolute zero, -459.6 farenheit is the lowest possible temp at which atoms transmit no thermal energy. therefore all objects above this temp emit thermal energy.

All matter (solids gas liquids) will show to a certain extent the following properties when light shines on them: transmission, reflection, absorption and scattering. the main one you want to be concerned with when it comes to how thermals work is reflection; because of this you cannot see through glass, water, metals, whereas with nightvision, (transmission of light) you can see someone behind a glass structure.

next thing would be atmospheric turbulence, ie your direct line of sight through air near heated surfaces like a hot sunny day across the surface of the desert. Only solution would be to change your LOS ie move to higher ground.

With all this in mind and to answer #1, thermals work by looking at sources that EMIT energy which is why you can see through misty conditions where as with nightvision you're looking at REFLECTING enhanced energy and can't see through the smoke.
Now depending on other atmospheric conditions you may or may not see a degradation in your image, but most likely you're not spending your time out in the field where its pissing rain and heavy fog sets and wind blowing out of control. If you are, you need to get checked out.

Now with #2 like dingdong said, it really depends on what type of optic you have. Some are hand held, some have simple reticles built in, some can be handheld and mounted in front of your optic. Those that you can mount in front of your optic may or may not allow you to use the reticle of your day optic (IE acog). That is why there are some military spec grade reticles out there with the "nightvis" illum feature to be used cohesively with the optic.

I hope this gives you a better understanding.
 
#18
dbateman said:
Bump.. Didn't want to start a new topic and it's on topic.

I've been thinking of getting a thermal viewer but I'm a little unsure of how effective it would be I just went outside at 2030 and measured the ground temp it's 32*c (89*f) am I correct in thinking that I will not be able to see most animals because of the ground temp ?

I looked up the average temp of a pig and its 38.7-40 °C (101.6-104° F) is that enough of a temp difference to detect pigs at night ?
Or would I be better off sticking with NV ?
.
Click to expand...

dbateman,

read my post and if you were to go hunting in the snow, you would see EVERYTHING because of the huge contrast in heat differences.
 
#19
[SUP][/SUP]
GhengisAhn175 said:
dbateman,

read my post and if you were to go hunting in the snow, you would see EVERYTHING because of the huge contrast in heat differences.
Click to expand...
I've got a FLIR ps32 and nothing hides......nothing, during the day or night. If it's a rabbit or elephant you can see it. I use it for detection and my helmet mounted PVS14 for identification. It's a great accessory to have hanging from your neck. Look at skypups pics above and you'll be amazed.
 
Last edited:
#20
Comparison of Thermal Vision, Unaided Vision, and Night Vision

stag said:
Thermal imaging - 2 Questions

1/ I've been told that thermal imaging works reasonably well in misty conditions, the lens on my image intensifier form a moisture layer on the front lens which degrades the image, does this have a negative effect with thermal imagers.

2/ I'm intrigued to know how you zero thermal weapon sights, my normal zero distance for a image intensifier would be 200yds does anyone have any "hot" tips!
Click to expand...

Stag,

Water, like silica glass, is highly opaque to thermal sensing -- both substances limit / block thermal radiation (in the wavelengths detectable by most thermal sensors) from passing through. Water will absorb, while silica glass will reflect the thermal radiation. So, yes, if condensation forms on the objective lens of a thermal scope, it will degrade the image.

If you use a "clip-on" thermal imager, you need only to establish "zero" on (i.e. boresight) the day scope that you are using with the clip-on thermal imager. The optical collimation on the thermal imager will allow the boresighting on your day scope's aiming reticle to be used.

-----
Enclosed below is a comparison of images of the same geography taken with different imaging technologies - thermal sensor at the top, night vision (Gen 3 Pinnacle light intensifier) at the bottom, and a digital camera (unaided) in the middle. These images were taken within seconds of each other on December 31 at around 11:00 PM, on an evening with clear skies but no moon, and which appeared very dark to unaided eyes.

The thermal imager (clip-on) is one that I had constructed on an ultra-high sensitivity, high-resolution, thermal core and which I have previously shared images from at this thread:
http://www.snipershide.com/shooting/snipers-hide-night-vision-devices/215301-thermal-vs-nv.html

The conditions (low temperature and low relative humidity) were close to ideal for thermal imaging. In the thermal image, note the detection of the power lines on the tree-line at the horizon, which is over 800 yards away. The power lines are just over 1 inch in diameter each, and are not visible during the daytime at this distance (or even 1/4 the distance), against the heavily forested background, with the naked eye, even under direct, bright sunlight.

The i^2 night vision image was seriously degraded by glare and blooming from street lights even though they were between 500 and 800 yards away from the view point.

The night vision scope, a PVS-14, and the camera lens used for the "unaided" photo, both have a much broader field of view (40-degrees), and therefore I joined two images captured from the thermal scope for the comparison.

IR-V

Compact image (thermal, unaided, night vision):

2n9e1bm.jpg


Large image (thermal only):

2m5dunn.jpg
 
Last edited:
#21
Last night I was out hunting with my thermal and there was a large adult raccoon walking in the water on the edge of the pond.

It surprised me to see two raccoons with the thermal, one was a mirror image of the real thing off of the calm waters surface, I had no idea that water would reflect a perfect thermal image at night (or during the day for that matter.)
 
#22
SkyPup said:
Last night I was out hunting with my thermal and there was a large adult raccoon walking in the water on the edge of the pond.

It surprised me to see two raccoons with the thermal, one was a mirror image of the real thing off of the calm waters surface, I had no idea that water would reflect a perfect thermal image at night (or during the day for that matter.)
Click to expand...

Skypup, like I said in my post above, the 4 properties (transmission, reflection, absorption and scattering). That you saw was reflection sir :)
 
#23
Thanks guys, so it seems ground temp has very little impact on how effective thermal imaging works.

So let me ask you guys this I'm looking at buying a clip on I can ether go with NV pvs-22 or similar or for a little more I can go thermal.
Would you go straight to thermal or would you get a NV clip on and latter on step up to thermal ?

This will be my first clip on. I have a pvs-14 that I use for walking around I'm just looking for a rifle mounted sight for hunting and shooting steel and the like at night.
I typically shoot in isolated places so there should really be no other light source other than what I am making.
 
#24
If you are not familiar with thermal, it is not a good thing to start off with. A long range NV scope and IR illuminator is way cheaper than any long range thermal system.

It really depends on your needs and the distances you shoot at, but I would not suggest thermal as a starting point, you will be able to ID your target much better with an NV setup.
 
#25
That looks like SWIR. That is far better than the $1,000,000 thermals I have looked through, but then again those have been phased out of service.


IR-V said:
Stag,

Water, like silica glass, is highly opaque to thermal sensing -- both substances limit / block thermal radiation (in the wavelengths detectable by most thermal sensors) from passing through. Water will absorb, while silica glass will reflect the thermal radiation. So, yes, if condensation forms on the objective lens of a thermal scope, it will degrade the image.

If you use a "clip-on" thermal imager, you need only to establish "zero" on (i.e. boresight) the day scope that you are using with the clip-on thermal imager. The optical collimation on the thermal imager will allow the boresighting on your day scope's aiming reticle to be used.

-----
Enclosed below is a comparison of images of the same geography taken with different imaging technologies - thermal sensor at the top, night vision (Gen 3 Pinnacle light intensifier) at the bottom, and a digital camera (unaided) in the middle. These images were taken within seconds of each other on December 31 at around 11:00 PM, on an evening with clear skies but no moon, and which appeared very dark to unaided eyes.

The thermal imager (clip-on) is one that I had constructed on an ultra-high sensitivity, high-resolution, thermal core and which I have previously shared images from at this thread:
http://www.snipershide.com/shooting/snipers-hide-night-vision-devices/215301-thermal-vs-nv.html

The conditions (low temperature and low relative humidity) were close to ideal for thermal imaging. In the thermal image, note the detection of the power lines on the tree-line at the horizon, which is over 800 yards away. The power lines are just over 1 inch in diameter each, and are not visible during the daytime at this distance (or even 1/4 the distance), against the heavily forested background, with the naked eye, even under direct, bright sunlight.

The i^2 night vision image was seriously degraded by glare and blooming from street lights even though they were between 500 and 800 yards away from the view point.

The night vision scope, a PVS-14, and the camera lens used for the "unaided" photo, both have a much broader field of view (40-degrees), and therefore I joined two images captured from the thermal scope for the comparison.

IR-V

Compact image (thermal, unaided, night vision):

2n9e1bm.jpg


Large image (thermal only):

2m5dunn.jpg
Click to expand...
 
#26
Delta4-3 said:
That looks like SWIR. That is far better than the $1,000,000 thermals I have looked through, but then again those have been phased out of service.
Click to expand...

Delta4-3,

I built this imager using an array of LWIR sensors. I realized, earlier in the year, that to gain significant improvements in image quality (from what is currently available in thermal weapons scopes for small arms), one would need to improve sensitivity below 30 mK and completely overhaul the lens technology.

IR-V
 
#27
I can't tell you how much that blows my mind. Impressive, and very well done!

IR-V said:
Delta4-3,

I built this imager using an array of LWIR sensors. I realized, earlier in the year, that to gain significant improvements in image quality (from what is currently available in thermal weapons scopes for small arms), one would need to improve sensitivity below 30 mK and completely overhaul the lens technology.

IR-V
Click to expand...
 
#28
SkyPup said:
If you are not familiar with thermal, it is not a good thing to start off with. A long range NV scope and IR illuminator is way cheaper than any long range thermal system.

It really depends on your needs and the distances you shoot at, but I would not suggest thermal as a starting point, you will be able to ID your target much better with an NV setup.
Click to expand...

Thanks Skypup thats pretty much what I thinking.
The thermal really impresses me, I didn't know they were available to us mere mortals.
I was looking for a PVS-22 when I stumbled upon a thermal sight thats when I started looking.


I'd like to hunt out to a few hundred yards and target shoot (steel) out to 1000yds, I don't know if thats a reasonable expectation but from what I have read I think I should be able to do it.
I think most of my night hunting with NV will be fairly close say inside 200yds.
 
#29
You could certainly use a handheld thermal scanner to detect your quarry prior to nailing them with your NV, a FLIR PS-32 will let you know if any mammal is within 500 meters of you....
 
#30
SkyPup said:
Last night I was out hunting with my thermal and there was a large adult raccoon walking in the water on the edge of the pond.

It surprised me to see two raccoons with the thermal, one was a mirror image of the real thing off of the calm waters surface, I had no idea that water would reflect a perfect thermal image at night (or during the day for that matter.)
Click to expand...

Water in the form of vapor, or as a mist or film of fine droplets, absorbs a large amount of long wave radiation directed at it. Water in solid form (ice) or liquid mass has more refractive properties with long wave radiation, but at a lower index than silica glass. The levels of refraction and absorption are variable across the long wave spectrum.

IR-V
 
#32
Thermal Resolution: Native Fauna, Alaska

Delta4-3 said:
I can't tell you how much that blows my mind. Impressive, and very well done!
Click to expand...

Delta4-3,

Thank you for your good words. This past weekend, I was in Alaska to participate in a cold-weather, disaster recovery, table-top (field) exercise. One of the most dramatic thermal images I captured, by random circumstance, was of a rabbit in the middle of an ice pack. To the naked eye and night vision, the rabbit was difficult to detect. However, my thermal imager was able to resolve a substantial amount of detail from 120 meters away. Ambient temperature was -20 degrees F.

IR-V

Black hot:

rtqn8l.jpg
 
#34
SkyPup said:
IR-V, you could have just stayed in the Midwest to practice cold weather disaster, it is warmer in Alaska than it is in Chi town today...

But great pic of that snow rabbit!
Click to expand...

Thanks, Skypup - I prefer the wildlife (and ad-hoc encounters with them) that Alaska has to offer! ;-)

No offense to residents and fans of the Windy City - I am alumnus of the University of Chicago.

IR-V
 
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