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(meteorobs) more on Ursid observing alert

Folks,

First, I think it indeed would be very wise to keep an eye on the Ursids
this year.

In addition, I want to point out that Ursid outbursts are NOT restricted to
years when the comet is in its aphelion, and that at least one to two (and
possibly more) outburst have occurred since 1986. This stream behaviour
certainly deserves more attention.

For example, in the early morning hours of December 22, 1996, both
IMO-president Jurgen Rendtel observing from Potsdam, Germany, and me
observing from Voorschoten, the Netherlands, detected Ursid activity at
Zenith Hourly Rates of ~25 to 30, well above typical rates! This enhancement
was confirmed by the NASA Global Meteor Scatter network (and a report on the
visual observations can be found in the 1997 Int. Meteor Conference
proceedings). Our visual observations covered the period 3-6h UTC, but the
peak might have happened slightly earlier (and at higher rates). I observed
8 times as many Ursids that night as the previous night although observing
conditions (Lm, radiant altitude) were similar and the observing time
slightly less!

The NASA Global Meteor scatter network also detected high rates earlier, in
1995, but almost a full day earlier in solar longitude compared to 1996.
Thus, these outbursts scatter widely in solar longitude. Indeed, the solar
longitudes of the historic 1945 outburst observed by the team of Becvar, and
the 1986 outburst observed from Norway, differ considerably. Thus keep an
eye open during several nights from December 21 to 23.

- Marco Langbroek
  Dutch Meteor Society (DMS)

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Marco Langbroek                    private: marcolan@stad.dsldot nl
Leiden University                     work: m.langbroek@arch.leidenunivdot nl
Faculty of Archaeology
P.O. Box 9515                         website: http://homes.dsldot nl/~marcolan
NL-2300 RA Leiden
The Netherlands

"What seest thou else
  In the dark backward and abysm of time?"

William Shakespeare: The Tempest act I scene 2
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