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(meteorobs) RE: Eta Aquarid ZHR from Florida
For Adam's comment,
>...I don't think anyone is saying the rates for the
>Etas are visually any where near 100 per hour.
I was incomplete in my prior post. Actual observed Eta Aquarid rates from
Australia in 1980-81 were numerous in the 40 to 60 range, and one individual
was well above that.
For my final hour period of May 6/7 with 6 Eta Aquarids seen in sky 5.5 and
radiant elevation 25 degrees, I have calculated the 7.0-limit ZHR as follows.
ZHR = observed rate / ( LM correction factor X sin(radiant elevation) )
I see only half as many sporadic meteors in sky LM5.5 as I do in LM7.0. For
now I need to neglect the difference between sporadics and Etas, so the
correction will turn out too strong. So, here the correction factor is 0.5.
The sin(25 degrees) is 0.423. Thus,
ZHR = 6 / ( 0.5 X 0.423 ) ) = 28.
If I want the ZHR to be in an LM6.5 sky, I would see only 85% as many
meteors, or ZHR = 24.
From an LM7.0 sky, if I see a normal maximum of 15 Eta Aquarids in an hour,
ZHR = 15 / 0.423 = 35. For the LM6.5 ZHR take 85% of that, or just 30.
I don't have enough feel for Adam's perception yet so can't fully judge his
good Eta rates. The above calculations show why I regard ZHR 30 to 40 as
normal for the Etas. Two situations contribute to higher values : different
methods of figuring the ZHR and higher perception for meteors.
Norman
Norman W. McLeod III
Asst Visual Program Coordinator
American Meteor Society
Fort Myers, Florida
nmcleod@peganet.com
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