Exposing PseudoAstronomy

August 8, 2012

Podcast Episode 47: Image Processing and Anomalies, Part 1


This episode is finally out. Well, “finally” as in “on time.”

I’ll admit that when I initially thought up this episode a few months ago, I was going to talk about how you can’t do spectroscopy from a still photo of an alleged alien (as some have claimed to have done with Billy Meier’s stuff).

But, given all the “goings ons” with the lunar ziggurat in the last week or two, this episode has turned into a Part 1 where this part discusses the very complicated but very basics of astronomy images and all the processing and calibrating that we go through to try to make it the truest representation of what we would really see. The main sections of the 41-minute-long main segment are: Black & White Astronomical Ground Photography, Different Spacecraft Camera Types, Releasing to the Community and to the Public, Color Processing, Quick Recap, Crazy Claims, How to Spot a Potential Fake or Forced Anomaly.

Part 2 should (yes, should, not “will”) include things like dynamic range, curves and levels, interpolation, filters, sharpening, etc. More to-the-point about some recent “goings ons” on the blog. Hopefully a companion video will come out.

Also in this episode was a New News segment, Q&A, and Puzzler. Given that it’s a 52-minute episode, I forewent Feedback.

9 Comments »

  1. Great Episode as usual. It would be great in Episode 2 if you could give some comparison between the different quality CCD’s and the Eye. I was curious as to how the efficiency of the eye in gathering photon compares to these CCDs.

    Comment by Belgarath — August 11, 2012 @ 8:22 am | Reply

    • Thanks Belg. I hadn’t thought of that, but it’s something that I saw at a science museum at one point. Just two images of the same thing, but one was really dim and “this is what your eye sees,” and “this is what a CCD sees in the same time.”

      Comment by Stuart Robbins — August 11, 2012 @ 9:42 am | Reply

  2. Truly excellent episode. Really first class Dr Robbins. As usual I learned some “stuff.”
    Below is what kicked my interest and required me to be an engineer when I grew up..

    http://www.amazon.co.uk/gp/offer-listing/B0007J9QA4/ref=dp_olp_collectible/275-2043570-6191536?ie=UTF8&condition=collectible

    Yep, I was 3 and had just been taught to read by my Papa. What started you Stuart ?

    Cheers mate
    Derek James Eunson

    Comment by Derek James Eunson — August 12, 2012 @ 11:54 am | Reply

    • Thanks.

      What started me? Dunno, just always liked astronomy.

      Comment by Stuart Robbins — August 12, 2012 @ 6:36 pm | Reply

  3. I am only an amateur astronomer. But when I am asked why, I tell people that every child likes stars and dinosaurs – and I never outgrew stars. (Which I guess insults Paleontologists!)

    Comment by Hypatia's Daughter — August 14, 2012 @ 1:28 pm | Reply

    • No, I don’t think they are insulted. The will just observe that they “outgrew stars”.

      Comment by johanges — September 1, 2012 @ 1:18 pm | Reply

  4. Oh one more thing I’ve been wondering (dunno if this will fit into your discussion or not) There are several of the pictures coming back from Curiosity which are ‘White Balanced’ What exactly is that and why do they do it? Example here: http://mars.jpl.nasa.gov/msl/multimedia/images/?ImageID=4433

    Comment by Belgarath — August 14, 2012 @ 5:17 pm | Reply

    • Not sure if I’ll talk about that, so I’ll answer it here just in case. White balancing here is just like white balancing for any photograph – it’s re-balancing the red, green, and blue (or CMYK) such that the colors look the way you want them to. Usually this is so that something you KNOW is supposed to be white (red=green=blue) is actually white in the photo.

      Since the Martian atmosphere has a lot of rusty dust in it, it casts a red/yellow over everything and so even though the top image at the one you linked is true-color as it would look to your eye if you were on Mars, the “white balanced” one is where they adjusted the RGB so that white would look white on Earth.

      Comment by Stuart Robbins — August 14, 2012 @ 5:22 pm | Reply

      • I think I mentioned this in a comment on episode 48, but how the heck do you know what “would look white on Earth”?

        The martian light has a red cast (what a photographer on Earth would sloppily call “warm”), but probably not due to the “rusty dust” but due to the particle size of dust. Yeah, I know, particle size and pigment color are related aspects but we are talking transmissive versus reflected light. If the sky is full of soot particles from a fire, the light will get a red cast to it, even though soot is black (for most values of black). [1]

        So how do you calibrate the white? They can’t just put a white (or neutral grey) card on a spacecraft that is outdoors on Mars since it WILL be covered with red dust near instantly. I guess they carefully measured the transmissivity of the filters they use for filtering the red, green and blue pixels and knowing the spectral sensitivity of the CCD cells, compute it from that, but I’m actually not sure if you would perceive that as “white” if you stood there in person. Color and perception is so darn complicated that the brain gets it wrong all the time. There is even spectral aliasing in the human eye since the color receptors response curves (esp. red) are not nice bells curves. [2]

        So, back to my question—what is white? Have we put humans in a room with simulated martian light and simulated Mars-like objects and checked what they actually think white is? I wonder if an astronaut working on Mars for a few month would change what they consider white? I suspect it has at least been considered, since it will have HID [human interface design] consequences.

        Also, you mentioned that they used a Bayer array for the CCD. Is there an advantage to this compared to a CMYG array for Mars. CMYG arrays are a bit more sensitive all in all, but there is additional processing and interpolation to display it on an RGB display, so maybe something is lost. Is there a difference between CMYG and Bayer arrays for mineral classification?

        If these are too far outside the domain of this podcast, do you have a good source where I could dig for more info? I’m an amateur in this, but I once was within Δ (actually 𝜖) of becoming a professional photographer, and I have spent almost 30 years dealing with color computer graphics and HID so I have some general background.

        –j

        [1] I know my mother’s father’s father commented on the beautiful skies they got in Sweden after Krakatau blew up in 1883. The mechanism here is due to the tiny particles in the high atmosphere scattering shorter wavelengths, so small amounts—there was only so much of Krakatau to go around in covering Earth all the way to Sweden—can have significant effects.

        [2] There is a nice general overview of visual receptors vs. RGB representation at http://www.cs.auckland.ac.nz/~rklette/TeachAuckland.html/mm/BG41slides.pdf

        Comment by johanges — September 1, 2012 @ 2:20 pm


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