[meteorite-list] (sans objet)

[Murray Paulson]

HI VIncent:

First off, the meteor would not be dark, rather it would be white hot.
The dark spot is probably a camera contrast artifact. But I thought
that it would be interesting to do some calculations on the object.

Some quick back of the Excel envelope calculations.

I am not sure which video you are using for this analysis, but lets
assume that it is not a telephoto close up, and is a wide field focal
length, say 50 degrees. This would go along with cell phone cameras
and dash cameras and is just a guess. If the video was 640 pixels
wide, (compressed for Youtube) and we place the meteor at 30 km
distance then each pixel in the image is

video  width	50	degrees
640	pixels	
0.078125	deg/pixel	
0.001363538	radians	
assume a distance of 30 km		
40.9	meters/pixel	

Now the dark object seems to take up several pixels, so lets assume 3
pixels width. This would give us an object size of 120 meters, which
is closer to the size of the asteroid that was passing between the
earth and the moon on the same day.

If I go the other way and place a 15 meter object at 30 km, the math give us

15	m	
assume at	30	km
0.0005	radian angular width or	
0.0286	degree	
1.72	minutes of arc	
0.37	pixel	

With the same camera, we would have the body size as 1/3 of a pixel.

Now, the video may have been zoomed in, and so you can scale these
numbers by the ratio of the true field divided by the 50 degree guess.

Cheers.

Murray

On Sat, Feb 23, 2013 at 9:39 AM, Vincent . <meteorh3_6 at hotmail.com> wrote:
>
> Dear all,
>
> When a very big bolide is observed, some  witnesses explain the observation of "the" meteorite parent, just in front of bolide.
>
> I wanted to check this very  unknow phenomen.
>
> I decomposed  some video from Chelyabinsk bolide. One of them shows  a dark mass in front of the bolide!!! It seem rotating. The dark mass is visible during approx 1/2 second.  Some details are visible 3/10 second later during 2/10 seconds.
>
> With an exciting surprise, the end of path, 1 second later  show the fragmentation of two medium mass. One of them create a veritable "plume" in the sky. Perhaps the beginning of a rain meteorite?
>
> If this is really the explosion of a meteroite mass in sky and/or the real "asteroid" falling in the atmosphere,  then that's is the first time that  the phenomen is recorded!   I'll be  very happy to have it discovered.
>
> Photos are visible ==>       http://www.flickr.com/photos/93493758@N04/    Enjoy!!
>
>
> Kind regards
>
> Vincent
>
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