(meteorobs) Aurigid analysis

[meteors at eclipse.net]

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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