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Re: (meteorobs) Possible alert : Taurids


Robert>>With few bright magnitude markers in the sky other than Jupiter,
Venus, the
moon, and the sun, how do regular meteor observers estimate magnitudes
brighter than -3?<<

Robert, the moon provides several markers based on it's phase. A crescent moon
will put out a magnitude -6, a quarter moon a magnitude -8 and a full moon
around -12. Of course the light from the moon is spread out over a larger area
than that of a meteor. It's relatively simple judging magnitudes up to around
-6 using the brightness impression that Jupiter and Venus gives. Beyond that
it starts to become more of a range of magnitudes and a best guess. I usually
still base it on how much brighter I think it appeared than a -6? This is good
for up to around -8...then it gets really tricky. If you start seeing shadows
on the ground from trees, you now are given another yard stick in magnitude
estimates. This would indicate magnitudes in the neighborhood of -10 or above.
If the meteor appeared brighter than the light from a full moon...dot it may just
be best to say that it was around -12 or brighter than a full moon. Estimates
beyond that may be misleading...unless something drives you to estimate
upward. For example, I once saw a fireball that was so bright that it hurt my
eyes to look at it and actually had to shield my eyes with my hands in order
to look. I gave this a magnitude of -19, but it probably could have been
anything over about -15. 

Robert>>Incidently, I'm dissapointed to learn that the definition of a
fireball
includes magnitudes I'd always considered uncommon but not exceptional.  I'd
always assumed a fireball was an object that rivaled the moon for brightness
and stood a better than average chance of striking the ground.  Something
that would make the evening news.  Something that an avid observer might see
only a few times in a lifetime, if at all.  Is there a better term for this
type of meteor?<<

Out in the field, the term used for these kind of fireballs is usually a
mouthfull of Ooooo's and Ahhhh's with expletives...but in the newsmedia these
kind of objects are often referred to as Bolides. These are the one's that
produce sonic booms, and/or explode and fragment brilliantly. 
George Zay
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