(meteorobs) Aurigid analysis

[Alister]

Please know that I am not attacking anyone's results!

I was just questioning the validity of using the formula given an unusual 
magnitude distribution.
Because for an event like this, it may be that moonlight did not play much 
of a role, so that
people in worse conditions who saw no fewer meteors have a much higher ZHR.

As you noted, it will help when more data comes in, especially at the 
fainter end.

Regards,
Alister.
----- Original Message ----- 
From: <meteors at eclipse.net>
To: "Global Meteor Observing Forum" <meteorobs at meteorobs.org>
Sent: Wednesday, September 12, 2007 3:10 PM
Subject: Re: (meteorobs) Aurigid analysis


> The way the magnitude distribution works into the ZHR calculation is
> through the factor "r", the ratio of meteors in one magnitude class
> compared to the next.
>
> Sporadics have an r around 3.5 (3.5 times more 2nd magnitude meteors than
> 1st), most showers around 2.5 and bright showers around 2 or 1.9.
>
> In the case of a bright outburst with a lack of fainter meteors (which has
> not been demonstrated yet, but is possible) r could even be less than 1
> which could lead to the ZHR being lower than the observed rate.
>
> Such a determination will require analysis of a substanioal number of
> accurate reports, and will take some time. Hopefully, enough observers
> recorded and reported such data with magnitude distributions (rather than
> just number of meteors seen) so an accurate determination can be made.
>
> The formula used by the IMO is ((1+Hourly rate)*(r^(6.5-Lim Mag)))/Sine
> Radiant Elevation
>
> Wayne
>
>
>> Well, "ZHR" still makes sense, but I don't think my calculation in this
>> case accurately describes reality. The standard ZHR calculation accounts
>> for the magnitude distribution of the shower meteors. I used a value
>> presented by Jenniskens in 1994 (maybe that has been revised... I didn't
>> check), but the value isn't consistent with what has been reported for
>> this year's shower, which seems heavily weighted towards brighter
>> events. That's why I suggested that the value shouldn't be taken very
>> seriously. The actual activity distribution plot, combined with the fact
>> that the camera sensitivity is just shy of magnitude 2, provides much
>> more useful information about the shower behavior.
>>
>> Chris
>>
>> *****************************************
>> Chris L Peterson
>> Cloudbait Observatory
>> http://www.cloudbait.com
>>
>>
>> ----- Original Message -----
>> From: "Alister" <aling at telus.net>
>> To: "Global Meteor Observing Forum" <meteorobs at meteorobs.org>
>> Sent: Wednesday, September 12, 2007 2:35 PM
>> Subject: Re: (meteorobs) Aurigid analysis
>>
>>
>>> Indeed, nice work on the report.
>>>
>>>>> clear. The corrected peak ZHR works out to around 3000, although I
>>>>> don't know how meaningful that is when peaks are very narrow.
>>>>> Another measure was that the cameras detected about 50 meteors
>>>>> brighter than mag 2 during the one hour of significant activity.
>>>
>>> I apologize if this is a triannual question: "Does ZHR" makes sense if
>>> the population is skewed heavily into the negative magnitudes? The ZHR
>>> I thought was based on greater and greater numbers of fainter meteors.
>>> So a decent number of bright meteors implies a huge number of fainter
>>> ones. If the population of this stream is not typical, then a
>>> calculated ZHR could be very misleading.
>>>
>>> Good observing,
>>> Alister Ling
>>> Edmonton, Alberta.
>>
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