(meteorobs) Judging bolide brightness

[Matson, Robert]

Hi Doug,

Since the Moon is an extended source, it's often difficult to compare
the brightness of a bright bolide to it since the bolide is typically
more point-like.  Unfortunately, beyond magnitude -4.5 there isn't
anything "stellar" with which to compare -- at least not of the
natural variety.

But what about Iridium flares?  I've found these to be useful for
comparison purposes when judging bolide brightness against ones memory.
Iridium glints occasionally exceed magnitude -8, and can reach -9 for
those in the lower-altitude spare orbit.

--Rob

-----Original Message-----
From: meteorobs-bounces at meteorobs.org
[mailto:meteorobs-bounces at meteorobs.org] 
Sent: Friday, April 28, 2006 2:21 PM
To: GeoZay at aol.com; meteorobs at meteorobs.org
Subject: Re: (meteorobs) Beautiful fireball - space junk?


 Hola George and Marco
 
Thanks both for the messages and answers reguarding the (not) space
junk.  George, Maybe, -3 or -4 mag. can cast a shadow (I've seen this
with Venus on crisp no moon nights).  But, in this case the fireball was
as bright as a car headlight illuminating the the area around us.  The
astrophotographers were not all very happy in the middle of their
exposures.  Anyway, I said at least as bright as -6 magnitude - this was
a conservative estimate to be sure.  I should have quoted it as in the
range of -6 to -7 during most of it but it seemed at one point to be as
bright as a Full Moon, and certainly the lighting up of the sky in the
binocular I saw seemed as bright as a full moon since my line of sight
was at least 20 degrees away from the light path w thinghen they lit up.
Of course I was dark adapted so it is difficult to be too precise.  It
was an incredible fireball generally, but the fact that 700 observers
saw it.  
 
Thanks for the comments on color.  The consensus of others was that it
was deep green (malachite is the color favored), but I have to admit I
was alone at the time in posting thinking is had a hue of blue hidden in
the green.  Well someone else just mentioned they saw a bluishgreen at
lunch today, and he was a very astute observer...
 
Hope someone can file a report on this fireball, I'm a little shocked
that I am the only one reporting it so far...
 
Saludos, Doug