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I color of the sun

  1. Nov 11, 2017 #1
    I'm confused by these pictures.
    I understand that the picture on the right has had color "assigned" to it because we can see uv light but the picture on the left is supposed to be taken in the visible spectrum. why is it yellow/orange and not white? isn't the sun white? both of these images where taken by soho, which to my understanding is way outside of our atmosphere.
    sun_uv_visible_compare_3feb2002_soho_820x400.jpg
     
  2. jcsd
  3. Nov 11, 2017 #2

    jim mcnamara

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  4. Nov 12, 2017 at 12:33 AM #3

    davenn

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    yes by the spectrum, but that top right image in the link is false colour ( just in case the OP gets mislead by the green comment :wink: )

    the left and right are both false colours
    They use Orange in the left image for the same reason my solar imaging uses anything from orange to red .... mainly because it gives better contrast between the black sunspot/active regions and the surrounding solar disk and it is a hell of a lot easier to look at through the solar telescope than if it was a bright white which would be hard on the eye(s)

    The right mage is the Helium II ( 304 Angstrom) image and the orange for that just happens to be what they chose to differentiate it from the other images and their chosen colours ....
    https://umbra.nascom.nasa.gov/images/latest.html

    @nmsurobert , don't get hung up on the colours, you will even find they vary a bit between the 2 different spacecraft SOHO and SDO
    it's no big deal :smile:


    Dave
     
    Last edited: Nov 12, 2017 at 2:11 PM
  5. Nov 12, 2017 at 9:48 AM #4
    This makes a ton of sense. I'm not too worried about it. I was sure they had their reasons. But I'm first year teacher teaching an astronomy class and I can already hear a few students asking me what I'm asking you guys haha.
     
  6. Nov 12, 2017 at 2:34 PM #5

    davenn

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    best wishes with your astronomy teaching, it's an awesome subject with so many fields of interest
    Tho I have a broad interest in astronomy, my main interests are in solar activity and also how it affects the Earth

    maybe you would like to keep an eye on these 2 threads of mine .....

    https://www.physicsforums.com/threads/solar-imaging-and-techniques.925656/
    and
    https://www.physicsforums.com/threads/for-those-aurora-chasers-a-heads-up.923833/

    regards
    Dave
     
  7. Nov 12, 2017 at 7:19 PM #6
    thank you. when i entered college, i went into physics because i wanted to study the sun, ironically. i did about two years of quasar research in college so I'm not a complete newbie when it comes to astronomy. sometimes i stump myself though... like now.
    i will check out those threads. thank you!
     
  8. Nov 12, 2017 at 8:21 PM #7
    I believe the most accurate data would be a pixel location and an electron per second count. The light hits the detector and causes the electron to run through the circuit. A cosmic ray hitting a ccd detector would count as one photon same as a purple photon (400 nm) counts as one hit.
     
  9. Nov 12, 2017 at 8:47 PM #8

    Drakkith

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    How does this relate to the thread topic?
     
  10. Nov 12, 2017 at 9:17 PM #9

    russ_watters

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    What exactly do you mean by that? I've taken photos with a monochrome camera and colorized them, but it is nearly impossible to tell what is colorized and what isn't when looking at a visible light photo of the sun. Here's one of my eclipse photos, taken with a solar filter and a standard DSLR, with no editing -- it is only "colorized" if the filter makes it look yellow-orange:

    EclipseSample.jpg
     
  11. Nov 12, 2017 at 9:29 PM #10

    davenn

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    exactly, and right there is your answer
    and that top left image is likely to be either a) "colourised by the filter or b) colourised in post-processing or c) a bit of both

    my 2 new narrow band Ha (Hydrogen alpha) filters give the sun quite a red colour.
     
  12. Nov 12, 2017 at 9:50 PM #11

    russ_watters

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    Ok, fair enough; I just hadn't heard the use of the word "colorized" except to refer to post-processing.
     
  13. Nov 12, 2017 at 10:50 PM #12
    The thread topic was "color of the sun". Our eyes see color when several sensors in the human eye detect slightly different intensity. If you look at monochromatic light 570, 580, and 590 nm radiation you will see three different colors (assuming not color blind). If you look at 620, 630, and 640 you just see red. Every detector including eyes are in effect taking a black and white image. The color that you see is created because the signal from one sensor has a different intensity than the signal from another. Your brain assembles the difference into colors.
     
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