Iridium flare intensity

Ed Cannon (ecannon@mail.utexas.edu)
Wed, 07 Jan 1998 20:24:35 -0600

After some days of clouds and rain, the sky cleared this evening.  
>From outside my office, I was lucky enough to see a magnificent 
flare from Iridium 30.  Adapted Iridflar output for a "generic" 
Austin location (30.30N, 97.75W, 150 meters):

                      Iridium       Sun  Fl   Maximum Flare    Ir
Date UTC  Time UTC  Azm Al Rnge  N   Al  Mag  Lat.     Long.    #
-----------------------------------------------------------------
98- 1- 8  00:16:35  048 67  838  A   -6  -8   30.305  -97.712  30

Since the Moon was in easy view, I made a quick back-and-forth 
one-power comparison.  It appeared to me that the Iridium flare
was much more intense than the Moon's light.  I don't know the 
physics and/or optics to know what to make of that in terms of 
apparent magnitude.  Iridiums are nearly point sources, while 
the Moon is not.  In any case, I'd say that, in some very real 
sense, the Iridium flare was brighter than the Moon, which 
tonight is about 67 percent illuminated according to:

  http://saatel.it/users/lore/moon.html

Also saw 4 others sats (only a few bright passes tonight).

Ed Cannon
ecannon@mail.utexas.edu
Austin, Texas, USA