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From: TerryMoselaol.com
Date: Fri, 5 Nov 2004 19:33:50 EST
Subject: Extra Leonid activity in E Europe?

Hi all,


There is a good chance of some enhanced activity from the Leonid meteors, and 
over a week earlier than the main shower peak! Unfortunately we will NOT be 
particularly well placed to observe this: conditions will be best for observers 
in E. Europe & the Middle East.

The following prediction has been calculated by Dr David Asher of Armagh 
Observatory, one of the world's leading authorities on meteor stream dynamics.

On the late evening of Monday 8 November the Earth is predicted to pass 
through an old and diffuse trail of debris from the 1001AD perihelion passage of 
comet Tempel-Tuttle, the parent comet of the Leonid meteors, which normally peak 
around Nov 17.

Since the stream is so old it will probably contain mainly the smaller 
particles, which produce fainter meteors. Rates are estimated to be from 50-100 
meteors per hour in prime observing conditions. But this is the so-called ZHR, or 
Zenithal Hourly Rate, which is the number of meteors per hour which would be 
seen by an experienced observer, with the radiant in the zenith, in a perfectly 
clear dark sky. But unfortunately at least one of those conditions will not 
pertain for us!

The peak is expected to be at 23.30 UT so as the radiant (in the 'Sickle' of 
Leo) will not even have risen from most of Ireland by then, we will see very 
few meteors, if any, at that time. And the radiant will still be very low even 
at 01.00 (less than 10 degrees for most of Ireland), when this extra early 
activity is likely to be tailing off, so we will be lucky to see much happening 
from here at all. Observers about 50 - 70 degrees of longitude further East 
than Ireland should have the best view, as the radiant will be high up for them.

If the meteors were likely to be bright we might see some, as they could be 
visible even over the much greater distance which pertains when the radiant is 
low. But, reluctant as I am to dampen expectations, I doubt if we will see 
more than a few meteors per hour before about 00.30 or 01.00. Of course if the 
passage through the stream occurs an hour or two later than predicted, when the 
radiant if higher from here, we will see more - maybe about 10-20 per hour.

Since the meteors are likely to be faint,  it will be essential to observe 
from a very dark site to get the best view.  In particular look for a clear & 
dark East to Northeast horizon as the constellation of Leo will be rising in 
this part of the sky.

The later in the night, the higher the radiant rises for us, but according to 
the predictions the activity from this particular stream may be over by about 
01.30 at the latest.

The 'normal' peak of the Leonids should produce a reasonable rate of meteors 
(maybe 30-50 per hour actual observed rate in a dark sky for us) just before 
dawn on the morning of Nov 17.

Anyway, meteor showers can often produce surprises, so it will certainly be 
worth looking from about 23.30 onwards on Monday evening, through into the 
small hours  of Tuesday morning, if it's clear.

Good Luck,

Terry Moseley


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