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Re: (meteorobs) New Member Peter Stinson & Request fo




In a message dated 99-06-18 16:39:00 EDT, you write:

<< lew Gramer wrote:
 
 >BTW, Mr. Zay's exceptions to the criteria I mentioned all have validity. 
 Except
 however, that I have not heard of bright fireballs near the horizon 
 appearing
 foreshortened or seeming to "hang in the sky" the way a flare might. What 
 is
 supposed to produce this effect, anyone?<<
 
George K>> Lew:  I believe the effect George Zay referred to results thusly: 
given two 
 objects having the same true velocity, one nearby, the other quite distant, 
 the apparent angular velocity of the more distant object will be 
 considerable less than the nearby object.<<

 George, This is exactly what I'm alluding to. what you said above is correct.
 
 George K>>For example, if a meteor at a distance of 200 km were to appear to 
travel 
 10 degrees in one second, and you were to remove this meteor to a distance 
 of 2000 km, its apparent angular velocity would be reduced by a factor of 
 200/2000, or to 1/10th of its observed angular velocity ( to 1 degree per 
 second) when it was nearby.  By the same token, if the meteor had a visual 
 track of 30 degrees when it was seen from a distance of 200 km, it would be 
 reduced in apparent length by the same factor of 1/10th, or to 3 degrees 
 when seen from a distance of 2000 km, thus the "foreshortening" alluded to 
 by George.   It is all a matter of perspective.
 George Kelley<<
 
 This is also part of the cause for some distant aircraft lights or contrails 
(particularly those heading towards or away from an observer.) to be 
responsible for some UFO sightings. The lights or reflected sunlight off a 
contrail after sunset appears quite stationary or nearly so for a seemingly 
long time. 
GeoZay
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