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(meteorobs) Time of Leonid maximum
TIME OF LEONID MAXIMUM
Although models of the distribution of dust in the orbit of comet
55P/Tempel-Tuttle attempt to give an improved estimate of the time of the
Leonid maximum, it is well known that the passage of the Earth through the
node of the parent comet is a close approximation (within a few hours) to
the time of maximum.
The time of nodal crossing for 55P/Temple-Tuttle is found from the mean
solar longitude (2000) which is equal to the longitude of the ASCENDING
node (2000). This is from the osculating orbit of the comet when the
comet is at the DESCENDING node. This occured close to 1998 March 8,
the standard epoch used in the published orbits. The value predicted by
Yeomans et al (1996) of Omega=235.25808 (2000) is basically identical to
Nakano's recent calculation (including 1998 observations) of Omega
=235.2583 (2000). This corresponds to a time of 1998 Nov. 17 19.2h UT
and 1999 Nov. 18 01.3h UT, some half-hour before the times given by
Yeomans et al.
The statement (http://www.imo.new/news/leohints.htm) "The node lies at
omega=235.258 deg, and the Earth will pass the node at lambda=235.29 deg
which corresponds to Nov 17, 20h UT." is incorrect as at the node,
omega must equal lambda (solar longitude).
Rob McNaught
rmn@aaocbn.aaodot gov.au