Thermal specifications and what they mean

Darknight

Darknight

Member
I've been reading a bit about thermal weapons sights and was hoping some of you with thermal experience might be able to share your knowledge.
I realize and read frequently that thermal is good for detection and nightvision is the better method for target ID and the shot. I'm currently running a pulsar 19a handheld and a Nemesis 2+ QS and am pleased with my first NV hunting package.
In regards to thermal scopes, the Pulsar XD series of thermal scopes have caught my eye as have the Armasight Zeus line of thermal scopes.
In the arena of coyote calling with shots within 200 yards I am wondering if some of you can explain advantages/disadvantages of a larger objective lens (ie- 75 mm vs 40 mm on the Zeus line). Is the field of view smaller with the 75 mm vs the 40 mm objective? Is image detail better with the 75 vs the 40 or does the 75 mm lens detect heat signatures at a longer range?
Along another line, I see different numbers having to do with microbolometer (ie- 384 x 288) and display resolution (640 x 480). What do these numbers mean? Is one or are both of them having to do with image clarity? Here I'm starting to travel down the path of the discussion of identifying the coyote vs deer vs fox, etc.
I hope some of you with experience can chime in here so we can all learn from it and appreciate the advice.
 
I'm new to thermals, i have the armasight apollo 640 30 hz 42mm. So far identifying targets within 200 yds hasn't been an issue. I can easily tell the difference between deer and coyotes but yard dogs or foxes and coyotes are a different story thus far. One of my biggest challenges is determining distant to the target. It takes a lot of time to get comfortable with thermals, the pay off is worth it.
 
Thanks wabbit,
Do you have to manually NUC the Apollo? I see you're in Florida. What's the coldest temps you've used the unit in? What kind of battery life do you get with it? Do you have an external battery pack on it?

Thanks for weighing in!
 
Low forties so far on temps, I get about 4 hours on two batteries so I was having to change them during a hunt. I use it for scanning too so It's on the whole time. I recently purchased the extended battery pack which should fix this problem. I don't have to NUC it but have done it to see if there was any improvement so far it really hasn't made any difference, Giving it a few minutes to warm up seems to help the most. It will NUC on it's own from time to time and there's some improvement with clarity. I have it behind a Burris AR332 scope which seems to marry together very nicely. I have noticed the picture is a little grainy when viewing through the day scope and you can't see the battery meter or pallet information on the screen. But the great thing is I could spot a coyote the other night and identify him at just over 400yds. I could see him sit down, lay down in the peanut field, turn his head to look at other coyotes howling in the woods. It's pretty cool
 
75mm vs. 40mm referes to focal length. the larger the focal length, the greater the optical magnification. The primary tradeoff with larger lenses is a reduction in field of view (FOV). A really long focal length lens will be like looking through a soda straw. You'll be able to see farther, but with a narrower FOV. Sensitivity has more to do with the 1/F number of the lens. Similar to how vis lenses work, the smaller the number, the more photons (or light) can get thorough and the higher the sensitivity.

uBolo dimensions are basically the size of the array. 384x288 indicates an array with 384 pixels horizotnally and 288 vertically. more pixels won't necessarily produce a higher resolution image though. If you take a 640x480 system and apply a 2x ezoom, the image will appear the same as a 320x240. Given the same lens and pixel pitch (size), the higher pixel count array will give you more FOV at 1x ezoom. Have a look at FLIRs image comparison chart here: http://www.flir.com/thermoSightR-Series/rangeTest.html. YOu can see that the RS32 4x16 at 1x has a very similar image as the RS64 2x16 at 2x.
 
Originally Posted By: DarknightI've been reading a bit about thermal weapons sights and was hoping some of you with thermal experience might be able to share your knowledge.

The best way to find out about thermal is to rent a unit and field test it. These are very expensive and can make for expensive mistakes if you cannot return or exchange the unit.

http://www.ultimatenightvision.com/Rentals-s/1820.htm

 
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Appreciate the advice and will look into renting before I buy. The Armasights Zeus 640 line is a bit confusing for me to weed through. Some are Pro models (waterproof is only difference?), the only 75 mm Zeus 640 is in the non-pro model line whereas the Pro line does not have the 75 mm lens.
I'm thinking I just need to rent and look through these things in cold weather and decide based on real-life tests. Thanks again for the advice and I'll see If UNV will do rentals on multiple Armasight models as well as an OLED Pulsar scope.
 
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