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RE: (meteorobs) Fwd: Leonids: USA "vs" the Eastern Hemisphere
I observed with a friend from the Saline Valley, one mountain range removed
from Death Valley in the direction away from Las Vegas. I didn't attempting
to estimate sky darkness, but I'm assuming it was essentially as dark as at
the Arizona site since there was no cloud cover and no sources of light
pollution. We didn't attempt to count meteors, but at the peak I quit
trying to view as much of the sky as I could because it no longer seemed to
matter; wherever I happened to be looking was fine. Remind me, does ZHR
represent the number of meteors visible in the whole sky in a unit of time,
or the number of meteors visible within a single observer's field of view
within a unit of time? (Yeah, yeah, I know it's REALLY a theoretical
maximum corrected for all sorts of things) In my field of view the rate was
on the order of one per second at the peak, which would be 3600/hr. So,
even if my sense of time was dilated by an order of two, I agree that 1000
seems a very low figure, especially if ZHR represents a whole sky rate.
As an aside, this was the first time I observed a meteor shower from a
location where I had an essentially unobstructed hemispherical sky with
excellent visability right down to the horizon. I was surprised to find
that the activity near the horizon was always much better than overhead.
I'm assuming it is because an angular section through the atmosphere near
the horizon encompasses much more air than the same angular section
overhead.
A couple of other notes on my experience. There were 5 or 6 meteors over
the course of the night that detonated with a flash that lit up the ground.
I was looking at the wrong part of the sky for each and every one of them.
In two instances I saw the flash from inside my tent when I ducked in to
grab some warmer clothes (well, truth is I was considering going to sleep
and the flashes encouraged me to get the warmer clothes and go back out...).
The earthgrazers (I saw four) were amazing! Somebody on this list mentioned
seeing meteors falling like "tears" after dawn broke. I passed out around
5am, too soon for the effect, but I saw the same thing from just outside of
Mojave in 1998; at the time it reminded me of drops of liquid fire against a
pale blue sky.
-Robert Hayden
-----Original Message-----
From: owner-meteorobs@atmob.org [mailto:owner-meteorobs@atmob.org]On
Behalf Of Joe Rao (via Lew Gramer)
Sent: Thursday, November 29, 2001 8:11 AM
To: Meteor Observing Mailing List
Cc: Glenn Schneider
Subject: (meteorobs) Fwd: Leonids: USA "vs" the Eastern Hemisphere
In a message dated 11/23/01 11:39:59 AM Eastern Standard Time,
meteors@aon.at
writes:
<< I feel IMO will need to
correct the figure for the american peak from 1000 to roughly 2500. 1000
just seems a very low figure for what we saw from Mt. Lemmon. >>
I would agree with Jure. I wasn't on Mt. Lemmon, but 70 miles to the
south and east, just outside of Benson, Arizona. It seemed to me that at
around 11h UT (4:00 a.m. MST) we were seeing Leonids coming at the rate of
one every 1 to 2 seconds (highly subjective since I wasn't making any
specific counts -- I was chiefly involved in photography -- but it certainly
seemed to me that a rate of 1000/hr. would be too low for what we were
witnessing).
I'm also forwarding along an E-mail message from Dr. Glenn Schneider of
the University of Arizona. Glenn was on Mt. Lemmon for the peak. Within
his
E-mail he provides a graph of Leonid activity comparing data compiled at Mt.
Lemmon to Alice Springs. I don't know if the graph (imbedded within the
message) will come through on the meteorobs list, but from what the graph
shows, Arizona beat Australia with a ZHR of ~2700 to 2000.
-- joe rao
========== FORWARDED MESSAGE
Date: Tue, 20 Nov 2001 15:22:40 -0700
From: Glenn Schneider <gschneider@mac.com>
Organization: Steward Observatory
To: eclipsechaser@yahoo.com, jrbt@eclipsedot net, KOLODNY@Kolodny-Anteau.com,
moskowi@attglobaldot net, Skywayinc@aol.com, small.exoticexp@erols.com
Subject: Leonids: USA "vs" the Eastern Hemisphere
Well, looks like it may be a tie. It appears we had a higher peak
rate, but over a shorter interval...
[snip... Image]
Keep in mind the ZHR is integrated over an hour long window, so the
"instantaneous" rate at/near a peak which is much sharper (narrower)
than an hour can (and is ) much higher. For storms like this we really
need ZMR (zenithal minutely rate!). Clearly on Mt. Lemmon each observer
covering only part of the sky was seeing on the order of a couple a
second at the peak.
Looks like we all had a good show all around, but haven't yet heard
from Craig. Craig? Are you back?
Steve: FYI - The above chart is from the counts reduced by all
those guys clicking away and shouting "druga, druga...", etc.
during the morning.
-GS-.
[snip... "/Macintosh%20HD/Temporary%20Items/nsmail68.gif"]
------- End of Forwarded Message
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