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(meteorobs) Observations
Rocky,
>My question is - Is it too early to see Leonids? In the two
>nights I saw 4 meteors I thought could be Leonids.
Setting up limits for a meteor shower's activity period is not possible.
Early and late shower members are caused by particles whose orbits have
changed over a long time. The stream is just getting less and less dense,
the further we get from the shower maximum. Another thing makes it even
more hopeless to find THE first meteor of a shower: as a visual observer,
you can't unambiguously decide whether a meteor belongs to the shower or if
it was just a sporadic ligning up with the radiant. Hence, the meteor
shower activity does not vanish to zero when you're far off the maximum,
but reaches a certain noise level, the level of sporadic pollution.
The question whether or not the four meteors were Leonids turns out to be
irrelevant this way. Visual observers are able to notice a shower activity
distinctly when the activity is above 1 or 2 meteors per hour. This is
roughly the definition of the activity period in the shower calendar of
IMO. The Leonids are mentioned to start on November 14 there, and I
recommend to never report Leonids earlier than November 10.
On final remark: Note that quite a few sporadic meteors tend to emanate
from a very diffuse region at the apex of the Earth's motion. The Leonid
radiant is so close to that position, that the sporadic pollution will
affect a weak Leonid rate worse than a radaint with a large
apex-elongation.
Rainer Arlt
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Visual Commission
International Meteor Organization
email: visual@imodot net
Homepage: http://www.imodot net
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