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(meteorobs) fwd: Re: Iridium/Point Meteors
More info from the satellite watching experts....
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Original Text
From: "Eberst" <eberst@cableinet.codot uk>, on 9/26/97 2:49 PM:
To: smtp@netsrv1@servers[<seesat-l@cds.plasma.mpe-garching.mpgdot de>]
At 17:08 97/09/24 EDT, Wayne T Hally wrote:
> My biggest beef in satellite-land is the Iridium flares, since they
>resemble what is a rare meteoric event- the point meteor (one coming
>directly at you...hence no motion).
>
On the contrary, Iridium flares do show motion - the orbital motion of the
satellite at 792 km height, orbiting 14.34217 times/day, which at an
elevation
of 50degrees gives an angular velocity of 0.4236 deg/sec. Since the flares
last typically 10-20 seconds, the object will move 4-9 degrees across the
sky.
Also point meteors are unlikely to last more than 2 seconds, whereas the
Iridium
flares last 5-10 times that duration.
There are, however, other satellites that mimic point meteors much more
closely;
the "Midas" satellites for example - 61sigma 1, 61alpha-delta 1, 62kappa 1,
63-14A,
63-30A, 66-77A, 66-89A. These can give isolated, brief but bright flashes
which
along with their low angular velocity, will deceive the unwary observer. I
would
recommend that the meteor observer always takes a pair of binoculars to a
meteor-watch, so that the area where any such isolated flashes are seen,
can be
immediately inspected with binoculars. In the majority of cases, the
culprit
satellite will be seen crawling away at its more normal magnitude around
+8.
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best wishes Russell Eberst @ North: 55 degrees, 56 minutes, 55 seconds
West: 3 degrees, 8 minutes, 18 seconds:
43metres (150 feet) above sea-level
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