difficult daylight flare

richard.keen@kingsmarket.com
Fri, 13 Mar 98 19:06:32

                                  
 Flare (glint) watchers -
 This morning, I observed one of those daylight Iridium flares in which
the satellite is in the same part of the sky as the sun.  That makes
them rather difficult to see.  The Iridflar prediction:
 Ir  Date    Time     Az El Range  Sun    Flare  Vis Peak Stand  Obs
            MST(UT-7)        km  azi elev Angle  Mag  Mag  Mag   Mag
 25 98-3-13  9:34:45 135 56 914  130 34.3  0.33 -3.4 -6.7 -5.0
 25 98-3-13  9:34:46 135 57 912  130 34.3  0.10 -6.7 -6.7 -8.2   -4
 25 98-3-13  9:34:48 134 57 907  130 34.3  0.81 -0.1 -6.7 -1.6
 I staked out the location of the flare relative to some tall trees the
previous night, and observed the event with 7x50 binoculars.  I first
saw the flare at about magnitude -4 and rapidly fading, and within 1
second it was gone.  Note that the prediction has the flare dimming
from -7 to 0 in just 2 seconds.  I don't know if I caught the peak,
although I think that if it were much brighter than -4, it would have
been obvious a fraction of a second earlier.
 Next time I'm going to set up my 20x120 big binocs on a tripod aimed
at the flare point the night before, although the risk here in Colorado
is that you never know if it will be snowing by the next morning.  Snow
isn't good for optics.
 Cheers, Rich Keen
 Coal Creek Canyon, Colorado, USA (39.877 N, 105.391 W, elevation
2728m)