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Re: (meteorobs) Linearids observed!
Wayne,
Thanks for the detailed response. My point here, has been to try to show
that a single meteor observation is not so low value as is a common
perception. A lot depends on the accuracy of the trajectory observation
and resulting area of possible radiant (APR). Granted, 2 or more meteors
allow you to triangulate, and obtain a much smaller APR. (If I had 2 I
could have reduced my area from 160 deg^2 to maybe 30 deg^2). But, even
with my large APR, the calculations show the odds of a sporadic occuring
there is small.
You claim a 50 deg radius FOV, but I don't think any observer (certainly
not myself) will stare at the same spot. Normally, your eyes will be
rapidly scanning 20 degs or so around the center of FOV, even though you
may not be concious of that, so will gain a lot of area at the
periphery, maybe 10,000 deg^2 would be an average FOV.
My original calculation was a rough estimate. If I use a FOV around
10,000 deg^2, and also account for the fact that the radiant could not
have been at the origin of a 20 deg long track, so the APR drops to
maybe 4 x 25 degs, or 100 deg^2, the probability comes out:
(1-100/10000)^5 = 95.1% chance that no sporadic occured in my probable
radiant. Still, very small chance a sporadic accounted for my
observation.
Just to respond to a few specific points, below:
1.) I dont know why you need to adjust +/- 1 to my count for
"statistical analysis". I definitely saw one bright potential Linearid,
not 2 or 0.
2.) My sporadic rate was low, but probably just an anomaly. Most of my
sporadics were observed in clusters, with long periods of total absence
of meteors, and oddly they occured earlier in the evening.
3.) I am not saying my observation is "proof" of Linearid, just that its
highly likely to be one, from statistical analysis. Especially since it
falls in the time interval when 2 other independent observers reported 9
Linearids.
Sincerely,
Mike Linnolt
>>>
Wayne T Hally wrote:
>
> Mike replied to previous comments:
>
> My FOV was centered near Polaris, so the Linearid appeared just to the
> upper left of center, so I could trace the trajectory back to the bowl
> of the big dipper with high confidence.
>
> I am certainly not arguing that point.
>
> I also observed 5 Taurid and 4 sporadic, in 2.5 hours. My error in
> estimate of the Linearid trajectory was about 5 deg at the dipper (low
> in N horizon) and 3 deg at the origin of the track (at elevation 40
> deg). This is an area of sky about 160 deg^2, where the radiant could
> possibly be located. The total sky is about 20,000 deg^2, so the
> probability that 5 sporadic did not come from this area is roughly
> (1-160/20,000)^5 = 96.0%, and you would need to see 87 sporadics, before
> your odds were better than even to catch one with radiant in this area.
>
> There are some misconceptions here. You are only looking at your field of
> view (As is any other "sporadic" observer). This is approximately a 50
> degree radius, so your FOV is only about 8000 deg^2. You only observed 1
> possible LINEARID meteor. As a minimum in any statistical analysis, you
> must add +/- 1 to that, so at the very least your rate for possible
> linearids is 0.4/hr +0.8/-0.4. I also feel your method of calculating the
> odds is suspect, but I have to think about that more.
> 4 sporadics in 2.5 hours is a very low rate (1.6/hr) ...certainly not
> unheard of (I know) but low in any case so that the schochastic
> distribution of meteors would increase the potential errors. The expected
> sporadic rate at your LM would probably be more like 3-8 PER HOUR. In any
> case, the point is, that one meteor by itself, considering the questionable
> nature of the Linearids, and your low sporadic rate, proves nothing. It
> DOES NOT mean that the observation is wrong, or worthless. It means that it
> must be combined with other observations in order to possibly derive any
> statistical significance from the activity. That will require more analysis
> than can possible be done in the week before the Leonids!
>
> So, with my observation odds of only about 4% (I disagree, but have not
> calculated more accurate odds yet) of catching a sporadic in
> this spot, and given the fact we were near a nodal crossing of
> J3/Linear, this is very likely to be a valid Linearid observation.
>
> I would only argue with the term "very likely". It most certainly a
> POSSIBLE Linearid. But one meteor by itself proves nothing.
>
> Also, there were 2 other observers who reported a total of 9 Linearids
> between 10Nov 2323Z - 11Nov 0424Z, with no activity before and after
> this time span. My single Linearid occurred at 11Nov 0345Z, and none were
> seen after that time up to 0715Z, when I ceased observation.
>
> However there were higher rates reported on earlier days, but even these
> must be considered suspect until a full analysis has been completed.
>
> Again, I am not suggesting that what you saw was definitely not a Linearid.
> But one must use extreme caution in stating unequivocally that it IS a
> Linearid. It's just that when one is dealing with very low meteor counts,
> using large correction factors, and observers using different methods and
> having different skill levels, some major analysis must go on before
> "proof" that a shower exists can be claimed. If you want proof, then
> chopped meteor photographs, or intensified video observations, where
> radiant and speed can be determined to extremely accurate levels, are
> required.
>
> This corroborates my observation and indicates a small burst of activity
> around this time.
>
> That is certainly a possibility. However, it has not been proven yet, and I
> urge caution to all in interpreting the data reported so far. And on behalf
> of Rainer, I also wish to thank all those who were lucky enough to have
> clear skies and the time to observe and report their observations. It is
> the data from dedicated observers such as yourself which will allow us to
> unravel these mysteries.
>
> M. Linnolt
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