1. Whitebeard

    Whitebeard Senior Member

    A friend of mine has posted this on facebook
    [​IMG]

    We suspect a contrail. Dunno any more details other than it was taken in Bristol, UK sometime this evening.

    Any thoughts?
     
  2. Hevach

    Hevach Senior Member

    Seems too narrow for a contrail, remember the moon's only about half a degree of arc across. Possibly a utility line?
     
  3. Whitebeard

    Whitebeard Senior Member

    true, I've asked my mate for more info
     
  4. Henk001

    Henk001 Active Member

    Did some calculations. The line appears to be roughly 1/80th of the moon diameter. Assuming a diameter of a utility line to be 4 cm this means it is between 350 and 400 m away. When the height of the utility line were 30m above the ground the apparent altitude (of the utility line and the moon) above the horizon turns out to be 4 to 5 °. However, when the moon had that altitude yesterday it wasn't dark yet (roughly 4:30 PM). Besides, I would expect to see more then one line.
    On the other hand I agree that a contrail would appear much wider than this
     
  5. GregMc

    GregMc Senior Member

    • Agree Agree x 3
  6. Trailspotter

    Trailspotter Senior Member

    Not, if the photo was taken soon after moonrise, when moon is still low above the horizon. It probably was the case, judging by its yellow colour.
    Contrails at these low elevations could be more than hundred miles away. Here is an example from another tread here:
    [​IMG]
    https://www.metabunk.org/whats-the-farthest-distance-a-contrail-is-visible-at.t5628/#post-143478
    For comparison, the Moon at the same zoom level/focal distance look like this:
    IMG_3489.

    Therefore it can be a contrail. If the exact time of photo was known, it would be possible to test this hypothesis by the identifying the flight.
     
    • Like Like x 1
  7. Henk001

    Henk001 Active Member

    I have to adjust my opinion on the contrail explanation a bit, after googling around a little.
    [​IMG]
    [​IMG]
     
    • Like Like x 1
  8. Henk001

    Henk001 Active Member

    Soon after moonrise yesterday was around 4:30 PM. The background wasn't dark yet at that time. The photo must have been taken later at the evening. I've taken a lot of pictures of the moon and most of them show the moon to be yellow:
     
    Last edited: Jan 23, 2016
  9. Trailspotter

    Trailspotter Senior Member

    By "soon after moonrise" I meant about an hour after moonrise. When I was cycling home around 6:00 PM, the moon already was rather high and whitish.

    As I said above, the contrail hypothesis is verifiable provided the exact time of the photo is known. The moonrise in Bristol yesterday (January 22, 2016) was at 15:31 at 61° (ENE). The Moon elevation and azimuth at any time are also known/can be readily calculated. For example, at 18:00 they were 20° and 88° (E), respectively:
    Screen Shot 2016-01-23 at 10.16.26.
    http://www.timeanddate.com/moon/uk/bristol

    All one needs afterwards is to check the FR24 (or any other flighttracker) playback for planes in the Moon's direction, which were at a right distance from Bristol to pass across the Moon at a given elevation.

    PS For the time of 16:50 this private jet would be a very good candidate:
    Screen Shot 2016-01-23 at 10.52.05.
    The white line's heading corresponds to the Moon azimuth at the time, 75°, and its length is about 79 km (from the scale bar at the bottom right corner). This is close to the calculated length of 75 km from the plane altitude (43,000 ft = 13.1 km) and the Moon elevation, 10°.
    The aircraft of this type usually have thinner contrails compared to passenger planes.
     
    Last edited: Jan 23, 2016
    • Like Like x 3
  10. Whitebeard

    Whitebeard Senior Member

  11. deirdre

    deirdre Moderator Staff Member

  12. Trailspotter

    Trailspotter Senior Member

    You do not need a long exposure to take a picture of full moon with an ordinary camera at the focal distances, like in the OP photo. For example, for my photo of full moon above Exposure Time was just 1/640 sec:
    Screen Shot 2016-01-23 at 12.56.09.
     
    • Agree Agree x 2
  13. Trailspotter

    Trailspotter Senior Member

    Here is a similar photo taken on September 27, 2015 from a similar general location:
    [​IMG]Supermoon Rising by Tristan Martin, on Flickr
    PS From the Planefinder.net playback, this trail probably came from one of the three flights at the bottom right corner, all by B737: Thomson BY3710 at FL410 (left) and Ryanair FR3212 at FL370 (my favourite candidate, middle) and FR3901 at FL310 (right):
    Screen Shot 2016-01-23 at 20.41.04.
     
    Last edited: Jan 23, 2016
    • Like Like x 4