Re: Unknown "Blinker" Last Night (LES 8)

From: Mike McCants (mmccants@io.com)
Date: Tue Sep 20 2005 - 15:58:29 EDT

  • Next message: Leo Barhorst: "LB obs 20005 Sep 20"

    Brad Young posted:
    
    >Ed, can you or Mike check my positions and see if that was indeed LES 8?
    
    Yes, your positions match the predicted position for LES 8 very well.
    
    >Timings(UT) 2:09:16 2:11:14 2:13:11
    
    >First 3 observations 1X (naked eye) then switched to 10X50 binoculars.
    
    Ed told me that the time of maximum brightness last night was about
    1:58 UT here in Austin last night.
    
    My conclusion is that the flashes are generally northwest/southeast in
    direction and the flashes will move northeast over time.  So the fact that
    you are 400 miles north and a little east of us would explain the fact
    that you observed flashes 12 or 14 minutes later than Ed did.
    
    >Magnitude (approx) +2.5 gradually declining to +7 on last one, except
    >"secondary flash" was also ~+7 mag.
    
    We failed to see secondary flashes a week ago and so we have not
    looked for them since then.
    
    >and I'll try again tonight, earlier again to suit.
    
    I believe the brightest flashes occur about 12 minutes earlier each night.
    
    LES 8 is very nearly geostationary (but with an inclination of 10 degrees).
    So it is in almost the same position at the same time every night.
    But the sun is currently moving south about 0.4 degrees per day.
    So the reflections move north about 0.4 degrees every day.  At latitude
    30 degrees, this corresponds to about 190 miles.  So if we observe
    it to be brightest about 12 minutes sooner every night, the reflections
    must be 12 minutes later about 190 miles to our north that same night.
    (This assumes that the flash track is east/west.)  (There is also
    some effect from the satellite moving north/south, but it is currently
    being observed near the northernmost point in its orbit.)
    
    An analysis of the times of maximum brightness as seen from Austin
    from 9/8 to 9/20 indicate that the "normal" to the reflecting
    surface was going from RA 10Hr 17Mn, Dec +1.0 on 9/8 to RA 9Hr 27Mn,
    Dec -2.9 on 9/20.  This means that the spot of light across the
    Earth will move in a westnorthwest/eastsoutheast direction.
    
    The predicted time of maximum brightness is about 1:46 UT tonight
    for Austin.  Observers north of Austin would see maximum brightness
    about 2 minutes later for each degree north.  South of Austin would
    be 2 minutes earlier for each degree south (of latitude 30).
    Observers east of Austin (longitude 98) would see maximum brightness
    about 1 minute later for each 1 degree east of Austin.  Observers
    west of Austin would be 1 minute earlier for each 1 degree west.
    
    Mike McCants
    Austin, TX
    
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