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Re: (meteorobs) Perseids Aug. 11/12
At 21:31 12-08-97 -0700, you wrote:
>
>. Unfortunately, I think the novel
>experience of being under such dark skies skewed my magnitude data. When
>I did magnitude distributions for Perseids and Sporadics, the mean
>magnitudes came out to be 2.2 and 3.0, about what one should expect under
>magnitude 6.5 skies. Compare my data to Marco Langbroek's, posted here
>earlier. He apparently observed a very faint portion of the Perseid
>stream (mean magnitude 3.3???), but his sporadic magnitudes are right on
>track for his LM. I got a high number of sporadics, as I should have, but
>my magnitude distribution is disproportionately bright.
>
>Observations 1997 Aug. 11/12 Wes Stone (STOWE)
>White River Canyon, OR 45N 18' 121W 39'
>
>
Hello Wes,
One of the reasons why your Perseids were much brighter might be apparent
from George's mail: your observational period covered the (modest)
re-occurence of the 'new peak', during which the stream features more
bright meteors.
One thing that can happen when you, as you wrote, are not familiar to very
deep Lm's, it that you start to estimate meteors too bright. Might be
partly an explanation, don't know.
Note that the mean magnitude of observed meteors is highly dependant on the
Lm, reason why you should be carefull in comparing mean magnitudes of
observers. With a high Lm, you see more faint meteors and thus your mean
magnitude will be fainter than that of someone observing under lower Lm.
But in this case, our Lm was more or less comparable. I do perhaps have a
slightly better eye for faint meteors though. Such things are slightly
variable from person to person and such variation becomes most notably
apparent with high numbers of meteors under very deep Lm are concerned.
But one thing that was apparent to both Koen and me on 11/12 and Koen,
Erwin and me last night (12/13) was that we thought the number of bright
meteors disproportionate (most notably 12/13: don't have the data of this
night yet, just arrived home), especially the first hours of 11/12. Bright
meteors notably came in after 0h UT only, the period before most were only
of moderate to faint brightness on 11/12: and last night 12/13 meteors were
bright early in the night but predominantly faint during the later hours.
Don't know why. It is very well possible that the population index varies
over time.
IMO's visual handbook notes that the population index indeed does vary and
that around maximum the pop. index is slightly lower (i.e. meteors are
somewhat brighter on average). Since you observed closer to the annual
maximum, this could explain things too.
Anyway, it is a very interesting topic!
Marco Langbroek
Leonids-'98? A once (twice?) in your lifetime appearance! You can't afford
to miss it!
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