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Re: Looking for Meteorites with Infrared binoculars

Hello List, George, Linda, Bob, Jeff and whom else I missed...

Let me lend my 2 cents worth to this thread since it has drawn several responses.  As you would believe or not believe, in my former career, I was a night vision device specialist.  So a quick lesson in common technologies used now and in the past. There are three technologies commonly used.  Light amplification, Infra-red (IR) Illumination, and Thermal Imaging. The first two are not better then day vision for detecting meteorites, as far as I can see.(no pun)

LIGHT-BASED SYSTEMS
 Light amplification is  a" starlight scope"aka image intensifier-- the source of the green night video on CNN.   It works with existing visible wavelengths which are too faint to see with the human eye. I have one for my camera and a set of night vision goggles. When they are working... they are a great viewer for meteors, probably detecting a +20 to 30 magnitude..  These are the most commonly available commercial items of the three technologies,  but misinformation leads some to believe these are thermal capable and they are not.

 The IR (Infra-red)Illuminator is a device for converting IR wavelengths to a visible wavelengths (the original Army Sniper scope). It depends on an infra red emitting  source (lamp) which is filtered to remove visible wavelenghts. .  This was used because the human eye can't detect the IR and was therefore "invisible" to potential targets. This technology DOES NOT detect heat.

FLIR and Thermal Viewers.
  The technology George is referring too is a thermal viewer aka FLIR ( Forward Looking Infra-Red). Thermal devices detect infra-red radiation via temperature differences.  They do not specifically register infra-red light wavelengths but deeper infrared wavelenghts beyond what we know as light.  FLIR detects heat differences in a scene. The detector chip is supercooled and the lens system is a special glass which allows infrared to pass thru. FLIRS can be used night or day.  They DO NOT detect lights,  but can sense the hot filaments of a light bulb.

 As you have it, metallic masses have different heat loading/storing abilities than do soil and rock. Light bodies and dark bodies have different heat absorbing abilities, as well.  With respect to armored vehicles, the major "heat emitters" for them are  the engine,  exhaust, and weapons. By far, it is solar loading which heats them the most. ( Sorry, but the vehicle mass is such a big heat sink (calorie absorber) human cargo is scantly discernible-- even at the average human body BTU rate)  

As I alluded to earlier, a mass has a certain heat absorbing, radiation, and storage ability.  This difference is key to using the FLIR for meteorite detection work. Hot is bright red  light  in the viewer and cold is black or dark .

 FLIRs don't detect absolute temperatures so much as they detect temperature differences. Metals absorb heat faster and re-radiate it sooner then rocks. However, because of the relative internal storage capacity of metal, it stays warmer longer in terms of heat differences, as compared to an equal mass of rock. Metals fluctuate more quickly and  more widely than nonmetallic rocks do.

 So in early morning, metals show up cooler/darker but heat up quickly. By mid to late day, rocks have a can have a slight hedge on metals because they are not taking  heat much below their surface and  are re-radiating more of the infrared energy falling on them. Metals take heat uniformly into their entire mass.  Early evening, there is a cross over again and rocks cool quickly.  Metals, however, have carried more heat inward and now have more stored energy to radiate back out.   As the thermal viewer is concerned,  metallic objects will stay warmer longer then their rock counterparts.  So by morning-- metals will be initially  darker, having lost more internal heat then nearby rocks.  At night, they will stay hotter or brighter longer, relative to the background.

TESTING:
There are firms who rent FLIRs at reasonable prices-- also some sold to big game trackers. If I were wanting to test a FLIR  for usability in meteoric iron detection, I'd set slag masses out at different ranges along with equal sized nonmetallic masses and note the differences throughout the full day and night . It is elaborate but may be feasible and the key to use is PRACTICE.
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