Water vapor imaging

Discussion in 'Physics' started by pyroartist, Oct 9, 2015.

  1. pyroartist

    Thread Starter New Member

    Oct 9, 2015
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    Has anyone seen images in which the water vapor has been made visible by image processing or dual wavelength comparison?
    I am wondering if the following method would work: Take an outdoor, daytime image through a bandpass filter at any wavelength
    in the near IR that is not affected by water vapor, such as 850 nm. Immediatly take another image of the same scene at the water
    vapor absorption wavelength of 940 nm. Find the difference between each pixel in the two scenes and scale to create a new image.

    Despite the fact that this seems an easy and interesting experiment I can find no record of anyone ever trying this and I
    don't want to purchase the expensive filters if it does not work.
     
  2. nsaspook

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  3. pyroartist

    Thread Starter New Member

    Oct 9, 2015
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    I should have mentioned that my intended experiment would be looking horizontally from a mountain top as opposed to satellites that look downward. Also I am concerned with finding small areas of increased water vapor such that I don't care much about what occurs beyond about 2000 feet away. Being an amatueur means we have to stick with the 940 nm band as the mid-infrared and far infrared requires much more expensive sensors.
     
  4. nsaspook

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  5. GopherT

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    Check ebay, some ir camera filters are available for $8.

    I am not sure how easy/difficult this would be. You will get some issues from camera movement. Have you tried looking at the difference of two photos taken seconds apart? How close are they to pure black? That would be interesting test to see how much effect is from camera movement vs filtering.

    Anyhow, you may also have problems with the filter because your lenses may already have some amount of ir and uv filtering.

    Good luck and report back any success/failure. I'm interested.

    How will you process the difference between the two photos? Is there software available or will you write it?
     
  6. pyroartist

    Thread Starter New Member

    Oct 9, 2015
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    There are a few free programs out that can subtract images. The only one I have used is Image Magick. It seems quite slow on some operations and has a clunky, command line interface, but it works. If someone has a better one please let me know.

    I have such a picture such as you described as a test but can't locate it right now.

    Most inexpensive consumer cameras do not have an IR filter to exclude IR light. To make a quick check look at
    the output of your TV remote control in the LCD viewfinder of your digital camera. It will show up as a bright white spot.
     
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