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Re: (meteorobs) Request for data
Thanks for posing an intriguing set of questions to the list, Jim!
At 08:04 AM 12/3/97 -0600, you wrote:
>There are two methods which might be used to obtain
>absolute magnitudes, each with their own disadvantages:
>
>(1) Observer determines his limiting magnitude from stars at the
>zenith, and judges all meteor magnitudes by comparison to this area.
>
>(2) Observer determines limiting magnitude from stars within the
>field of view, and judges meteor magnitudes from stars in this field.
>
>Method (1) was used more frequenctly in the past, while method (2) is
>the most commonly used today, though I have still heard a few observers
>on this list reporting their limiting magnitude from zenith stars.
In fact, according to discussions on meteorobs last year, the "standard"
IMO method (and so possibly the one used by the majority of observers
here?) is actually the first! I began by using LM count areas SCATTERED
around the sky, with the idea that these would average out any variations
in LM across the sky due to high atmosphere haze, light pollution domes,
twilight, etc. But I was quickly corrected by more experienced readers of
meteorobs, that IMO LM count areas should in fact be chosen as close to the
ZENITH as possible! So how about it, guys: is this the method used by most
IMO observers now?
Regarding the two methods of meteor magnitude estimation, I have to admit
that I actually regularly use both! It could be because my
magnitude-estimating skills are not practiced enough to be "innate" yet,
but I frequently find myself correcting magnitude estimates by doing
comparison with stars NEAR where the meteor was observed. In fact, as my
knowledge of good comparison stars around the sky grows, I actually do this
MORE often. (Of course my technique for fireball magnitudes is yet more
complex, but leave that out for now!)
I think the analysis you're attempting will end up being complicated by
this mixture of observing methods, Jim. I'm not sure how widespread the
combined "comparison and impression" technique is among more experienced
observers, but I would imagine that many more inexperienced (or less
frequent!) observers find it necessary to "calibrate" their estimates
frequently in this way. I'm not at all sure how you could correct for this
either, unless you rely exclusively on frequent, highly experienced observers.
Lew