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  1. Mick West

    Mick West Administrator Staff Member

    [​IMG]
    A contrail and a cloud layer. It looks like it was above it casting a shadow, and then changed to below it. I'm not entirely sure. Kind of odd as you'd think it would be climbing. So is then shaded by the cloud layer, and then brightly lit above it?
    1:39PM PST, 21:39UTC,
    Plane is flying from bottom right to top left, i.e east, away from the sun.
     
    Last edited: Dec 12, 2016
  2. SR1419

    SR1419 Senior Member

    Any chance the dark part is a distrail?
     
  3. Mick West

    Mick West Administrator Staff Member

    I took video I'll upload it shortly, but it showed my identification was incorrect. It's a Q400 prop tip contrail at 25,000 feet. Even better!!

    20161212-140636-nq62u.

    20161212-141130-jnbix.

    Alaska 2586
     
  4. Mick West

    Mick West Administrator Staff Member

    There's a middle bit between the dark and light that seems to be a distrail, but I think the dark part is actually just the contrail below the cloud layer, so essentially in shadow.
    20161212-142300-orueo.

    20161212-142417-yzt9f.
     
  5. Mick West

    Mick West Administrator Staff Member

    • Like Like x 1
  6. Mick West

    Mick West Administrator Staff Member

    • Like Like x 1
  7. Trailspotter

    Trailspotter Senior Member

    I think that all of the contrail is probably below the cloud layer. The cloud layer creates an uneven background, both in optical density and illumination terms. To the observer, it is appears denser closer to the horizon because of the viewing angle, and it is much brighter around the sun because of Mie scattering being predominantly in the forward direction. Against denser and brighter background, the contrail appears darker, but against less dense and opaque background higher in the sky, the contrail looks brighter.
     
    Last edited by a moderator: Dec 12, 2016
  8. Mick West

    Mick West Administrator Staff Member

    Possible, it seems like a more abrupt transition than I would expect though. But also there does not really seem to be any disruption of the cloud in the suggested "distrail" part.
     
  9. Mick West

    Mick West Administrator Staff Member

  10. Mick West

    Mick West Administrator Staff Member

    Panorama showing more of the trail at once.
    Pano_IMG_1783=aw.
    This has beenadjusted to bring out more detail and resized to 1920 wide. The full sized unadjusted pano is attached as a .ZIP
     

    Attached Files:

  11. Trailspotter

    Trailspotter Senior Member

    Last edited: Dec 13, 2016