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Re: (meteorobs) Leonids

In a message dated 10/27/2000 6:16:36 PM Eastern Daylight Time, 
rendrag@earthlinkdot net writes:

<< I noticed my calendar has the Leonids on the night of 16/17 Nov. at
 midnight.  That was based on the IMO calendar for 2000 which has the
 lambda at 235.27 degrees which according to my table is 8 UTC on the 17
 th.  

    This peak time was "probably" based on the time that the Earth will cross 
the descending node of the Leonid parent comet, 55P/Tempel-Tuttle.  That 
comes at 8:05 UT on November 17.  Traditionally . . . before the dust trail 
method of meteor shower prediction became popular . . . it was common to 
anticipate the greatest meteor activity to occur around the time of the nodal 
crossing.  Interestingly, some minutes before nodal crossing -- at 7:53 UT on 
November 17 -- the Earth is expected to pass to within 0.0012 AU of a dust 
trail that apparently was expelled by the comet in 1932.  This "could" 
produce a brief, albeit significant meteor outburst. 

     The more recent data has 3:44 UT and 7:51 UT on the 18th.  I am
 assuming that this later date is the more nearly correct since it is
 current data from Asher and McNaught.
     However I assume that neither of these times favor the US West Coast
 since the radiant will just have risen by the second of these times.
 However no one will avoid the moon since it appears to rise very near
 the radiant.  Correct me where I am wrong.

    You are quite correct.  The 3:44 UT trail (according to Asher and 
McNaught) was expelled from 55P/Tempel-Tuttle back in 1733.  Meteor 
visibility will be limited mainly to the Eastern Hemisphere.  The 7:51 UT 
trail was shed by the comet in 1866.  While much of North America should be 
able to view any activity from this trail, the eastern part of the continent 
is favored.  Along much of the west coast of the US, the altitude of the 
Leonid radiant will be less than 10 degrees above the horizon (as compared to 
35 to 45 degrees along the US eastern seaboard).    

-- joe rao
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