[meteorite-list] Wales images, trail orientations

From: Matson, Robert <ROBERT.D.MATSON_at_meteoritecentral.com>
Date: Thu Apr 22 10:28:22 2004
Message-ID: <AF564D2B9D91D411B9FE00508BF1C86901B4EDD3_at_US-Torrance.mail.saic.com>

Hi All,

Okay, I think I can finally close the book on this Wales event,
at least to my satisfaction. I've got a solution (actually
a family of solutions) that within the uncertainties of the
camera pointing knowledge/orientation and the observer locations
points to an aircraft contrail at an altitude of < 30,000 feet
traveling on a heading of azimuth 261 passing about 5.3 km south
of Porthcawl. This produces an apparent trajectory that is
slightly steeper as seen from Porthcawl than Pencoed.

I actually think the Porthcawl image was taken later than the
reported 19:13 BST. At this time, the sun was less than one
degree below the horizon, and the sky is just too dark for this
to be true. I wouldn't be surprised if the picture was taken
closer to 19:30. If the picture was truly taken at 19:13, much
more of the track would have been sunlit.

In response to my last message, Marco asked:

> ... I do not quite follow your argument about the angles
> (which might however be my mind putting me off only). To me,
> it is clear that with a trail to the west of Porthcawl,
> Pencoed which is even more to the east should see it at
> a flatter angle. Hold a ruler next to the left of your head
> to mimic the trail as seen in the Porthcawl image. Then move
> your head to the right while keep looking at the ruler.

There's the flaw with your analogy -- moving your head to the
right means moving your location north-northwest since you are
facing west-southwest. The Pencoed location is actually almost
directly behind you. A better method is to draw two dots on
a map representing the two locations, and a line under both of
them at various tilts. Keep in mind, the line cannot be east-
west -- it must tilt somewhat south of west. What you'll
discover is that if the tilt is more than 15 degrees (azimuth
255), the track must come closer to Pencoed than Porthcawl,
and we know this isn't the case because the trajectory is
flatter as seen from Pencoed.

Cheers,
Rob
Received on Sun 05 Oct 2003 05:28:44 PM PDT