Thermal and preparedness.

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  • BrianS

    Active Member
    Apr 26, 2010
    415
    Both thermal and NV aren't in the budget to get both at once, but which one is better to start with? Budget would be 3-4K for each.
     

    steves1911

    Ultimate Member
    Dec 2, 2011
    3,004
    On a hill in Wv
    Both thermal and NV aren't in the budget to get both at once, but which one is better to start with? Budget would be 3-4K for each.
    Thermal...it won't give you the identification at range that a good NV will but guaranteed it will detect things you would have never noticed with just NV. Thermal works In daylight too.
     

    BrianS

    Active Member
    Apr 26, 2010
    415
    Thermal...it won't give you the identification at range that a good NV will but guaranteed it will detect things you would have never noticed with just NV. Thermal works In daylight too.
    Good point. I'll head down the rabbit hole of information and try to narrow down the pile of thermal options.
     

    Archeryrob

    Undecided on a great many things
    Mar 7, 2013
    2,964
    Washington Co. - Fairplay
    Got mine today. Only got to mess with it for a few min but pretty cool for the cost. At about 80 yards up the driveway I could still make out most things. It doesn't appear to look through windows well. Had to go outside because all I kept seeing looking through the window was a black screen.
    InfraRed wave lengths bounce off of glass.
     

    smokey

    2A TEACHER
    Jan 31, 2008
    31,244
    Both thermal and NV aren't in the budget to get both at once, but which one is better to start with? Budget would be 3-4K for each.
    Do you want to move around at night(nightvision) or detect warm-blooded things(thermal)? Those are the jobs each does.
     

    gwchem

    Ultimate Member
    MDS Supporter
    Dec 18, 2014
    3,416
    SoMD
    InfraRed wave lengths bounce off of glass.
    Technically, only a fraction bounce off, the amount determined by the refractive index at that wavelength and Snell's law. Most long wave IR (thermal) is absorbed by window glass. Exotic glass used in the lenses of your objective don't.
     

    teratos

    My hair is amazing
    MDS Supporter
    Patriot Picket
    Jan 22, 2009
    59,624
    Bel Air
    Do you want to move around at night(nightvision) or detect warm-blooded things(thermal)? Those are the jobs each does.
    I was thinking about this very thing on the way to work. Thermal for seeing if anything is out there. NV for navigating.
     

    smdub

    Ultimate Member
    MDS Supporter
    Nov 14, 2012
    4,609
    MoCo
    Technically, only a fraction bounce off, the amount determined by the refractive index at that wavelength and Snell's law. Most long wave IR (thermal) is absorbed by window glass. Exotic glass used in the lenses of your objective don't.

    Just about any bare metal or glass object has an emissivity of ~0 at IR. You can see your own reflection in glass and aluminum plate. We used FLIR extensively in the lab for testing. Very much like a mirror so I don't know how snell's law comes into it. For any aluminum heat sink in the lab that wasn't black anodized yet we'd just put a piece of scotch tape on it to be able to 'see' its temperature at that spot. You can not see a shiny metal object that is hot enough to burn you. Even hot raw aluminum can get to dangerous temps before really being able to detect.

    The lenses in our high end FLIR were Germanium. Its a crystal but I don't know that I'd call it 'glass' :) Opaque to visible wavelengths but transparent at IR. FWIW, per mass, germanium is about the same cost as silver.
     

    gwchem

    Ultimate Member
    MDS Supporter
    Dec 18, 2014
    3,416
    SoMD
    Just about any bare metal or glass object has an emissivity of ~0 at IR. You can see your own reflection in glass and aluminum plate. We used FLIR extensively in the lab for testing. Very much like a mirror so I don't know how snell's law comes into it. For any aluminum heat sink in the lab that wasn't black anodized yet we'd just put a piece of scotch tape on it to be able to 'see' its temperature at that spot. You can not see a shiny metal object that is hot enough to burn you. Even hot raw aluminum can get to dangerous temps before really being able to detect.

    The lenses in our high end FLIR were Germanium. Its a crystal but I don't know that I'd call it 'glass' :) Opaque to visible wavelengths but transparent at IR. FWIW, per mass, germanium is about the same cost as silver.
    You can use Snell's law to determine the amount of incident light that gets emitted through an interface or reflected. But it's simplified as a ratio of refractive index (real part of the permittivity). For something like aluminum, refractive index is extremely large at most wavelengths, something true of most metals. Glass is lossy, the light is absorbed instead of reflected, but in the end same effect to your optic.

    Technically, emissivity is not what we're talking about, where the inability to use thermal through glass is due to transmission. Emissivity is the relative amount of light given off by the material at that temperature.
     

    44man

    Ultimate Member
    MDS Supporter
    Feb 19, 2013
    10,069
    southern md
    So can people see when the or light is on with the naked eye at night?

    Can others with any kind of night vision see your ir light like a flashlight beam?
     

    RRomig

    Ultimate Member
    Industry Partner
    MDS Supporter
    Aug 30, 2021
    1,870
    Burtonsville MD
    You’re going to get a certain amount of night blindness from looking through the optic. I use the same eye for scanning as shooting so I have one good eye to see where the hell I’m walking. I also find white hot to be the easiest on my eye but I know people that like black hot better.
     

    teratos

    My hair is amazing
    MDS Supporter
    Patriot Picket
    Jan 22, 2009
    59,624
    Bel Air
    You’re going to get a certain amount of night blindness from looking through the optic. I use the same eye for scanning as shooting so I have one good eye to see where the hell I’m walking. I also find white hot to be the easiest on my eye but I know people that like black hot better.
    I prefer the white hot as well.
     

    steves1911

    Ultimate Member
    Dec 2, 2011
    3,004
    On a hill in Wv
    So can people see when the or light is on with the naked eye at night?

    Can others with any kind of night vision see your ir light like a flashlight beam?
    Ir is invisible with the naked eye but yes anyone with a NV will clearly see another IR light. A small ir strobe in a bdu pocket is visible from a long ways off with decent NV.
     

    erwos

    The Hebrew Hammer
    MDS Supporter
    Mar 25, 2009
    13,836
    Rockville, MD
    We messed around with the HS1 tonight, and it seems reasonable for the price. Good enough for scanning, anyways. I'll provide a 30mm QD mount and see how it is as a sight.

    Sent from my Pixel 8 Pro using Tapatalk
     

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