Re: Iridium 18 flare (Venus vs. Iridium)
Sat, 1 Nov 1997 19:55:14 -0500 (EST)

Comparing daylight Venus observing with daylight Iridium flares:

I saw a -6.1 Iridium daylight flare Friday and made a post earlier.
A few months ago, I tried to see Venus perhaps 1-2 hrs. before
sunset using 7x35 binoculars.  I didn't know *precisely* where to
look so was scanning around.  Finding it was difficult and tedious
and took some time.  Then once found, my thought was "Wow,
that's bright; why did it take so long to see it?"  Then I would take
the binoculars down to see it with the unaided eyes and couldn't.
Then binoculars again, more difficulty in seeing it but when found
again it seemed so obvious.  There are probably people on this list
who can explain why this happens in detail.  My thought is that it
is a combination of how the eye works (adjusts) to the lighting 
environment and the way the mind connects to the eye (if that 
makes any sense).

But since potential daylight Iridium flares will be much brighter 
(-5,-6,-7,-8?) than Venus AND with the movement of the satellite,
seeing an Iridium daylight flare with the unaided eye should be
a lot easier than seeing Venus with binoculars 1-2 hrs. before
sunset IMO.  You just have to be looking at the correct area of
sky at the right time and of course, block the sun.  It stands to
reason that the farther the sun is from the flare portion of sky,
the better.  In the case of the one I saw, the sun was only 3 
degrees above the horizon and was blocked by a building and
the Iridium flare was 72 degrees above the northern horizon.
I think that the movement of the satellite is a great factor in the
eye/mind picking it out against a bright sky. 

Jake Rees
Burbank, Calif., USA