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Reporting on the Leonids - PART I
=================================
Dear meteor enthusiasts,
The peak night of the Leonid meteor shower gets closer, and
I would like to emphasize some issues of reporting your
observations to the International Meteor Organization. The
global activity analyses of the Leonids and other meteor
showers is enormously successful. As every year, everyone
being out for the Leonids is invited to contribute to the
grand totals and the measurement of a precise cross-section
through the Leonid stream.
We can distinguish four groups of observations. Each of them
is most valuable for the analysis of the Leonid shower, you
may decide which version looks suitable for your observing
plans:
(i) Recording meteor counts per minute.
(ii) Recording Leonids/non-Leonids per minute
(iii) Recording Leonids/non-Leonids plus magnitudes
(iv) Recording LEO/TAU/AMO/spo plus magnitudes
During the time of the outburst, when more than say 50 meteors
per hour are visible, the majority of them are Leonids. The
error of simple counts (i) is thus small. In this first of my
messages, let's have a look at the first style:
Recording meteor counts per minute
----------------------------------
The following example is adapted from Lew's recent message about
reporting on the Leonids. Formats may be slightly different;
the important thing is that the report is complete and roughly
follows the below order:
==================
Observer: Tom KING
Place: Huntington, NY (Lat 40.8 N, long 73.4 W)
Time: 9:45-10:46, 19 Nov 2002 UT. [UNIVERSAL TIME = EST+5]
Effective time: 100% (no time lost to looking away or breaks)
Limiting mag.: +5.0 [measured by counting stars]
Field obstructions: none.
Direction faced: Taurus
--
ONE MINUTE COUNTS STARTING 09:45 UT
09:45 23 meteors
09:46 17
09:47 19 (10% cloud)
09:48 15 (30% cloud)
09:49 BREAK
09:55 18
09:56 25
09:57 22
...
==================
Observer: Only counts by single observers should be
reported. If you observe in a party of several
people, these observers should take their
individual notes on meteors, irregardless whether
two people saw the same meteor.
Place: Give a nearby town. Geographic coordinates can
be given as above, or as 40deg48'N, 73deg24'W.
Field obstructions: Usually this means buildings or trees. Note
that a typical field of view has a diameter of
little more than 100 degrees. If there is sky
blocking near the horizon and irrelevant for your
observing, keep 'none' in this line. If you have
cloud moving through your field, note the rough
percentage behind the minute counts (see above).
Direction faced: A constellation name is best here. If the field
center changed during the observation, note it
among the meteor counts. If you like to give RA
and DEC -- even better.
09:45 23 meteors: This one-minute count refers to 09:45:00 to
09:45:59 inclusive. Please make sure that you
have a precisely set observing watch.
Observations should be sent to namn@a...
for North American observers, and to visual@i...
for all other observers. Your reports then enter the global analysis
of the Leonid meteor shower.
If you have any questions, do not hesitate to discuss them here via
the meteorobs mailing list.
Coming soon: Part II, Recording Leonids/non-Leonids
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Reporting on the Leonids - PART II
==================================
This is the second of my messages about Leonid reporting.
The observational data will be more precise if meteors
not belonging to the Leonid radiant are sorted out. We call
these 'non-LEO'. Here is an example of the modified report:
==================
Observer: Tom KING
Place: Huntington, NY (Lat 40.8 N, long 73.4 W)
Time: 9:45-10:46, 19 Nov 2002 UT. [UNIVERSAL TIME = EST+5]
Effective time: 100% (no time lost to looking away or breaks)
Limiting mag.: +5.0 [measured by counting stars]
Field obstructions: none.
Direction faced: Taurus
--
ONE MINUTE COUNTS STARTING 09:45 UT
TIME LEO non-LEO
09:45 23 0
09:46 17 0
09:47 18 1 (10% cloud)
09:48 15 0 (30% cloud)
09:49 BREAK
09:55 18 0
09:56 24 1
09:57 22 0
...
==================
Leonid association
------------------
The radiant of the Leonids is the point from where all the
shower members seem to emanate. If you extend the meteor's
path backwards, and the extension meets the radiant point
at RA = 10h20m, DEC = +22, it was most likely a Leonid.
Most Leonids are very fast; near the radiant, however, they
can appear fairly slow and short. Meteors close to the radiant
must be short. A meteor of 10 degrees length at 5 degrees
distance from radiant is not a Leonid.
Meteors moving _towards_ the radiant, are not Leonid members.
At rates of say 20 meteors a minute, you will feel unable to
check Leonid association. It is entirely adequate to drop the
LEO/non-LEO discrimination then.
Difficult meteors
-----------------
You will see quite a few meteors at the edge of your field
of view. If you are not sure whether or not this was a Leonid,
count it as a Leonid. The reason is, that it is statistically
the more likely case that you saw a Leonid, because their
activity is higher than the non-LEO activity.
The non-LEO activity will be roughly 0-3 meteors in 10 minutes
given the lunar conditions this year. While observing, if you
notice that you regularly log more than this, you should be
less restrictive with Leonid association.
Send data from...
-----------------
North America to .......................... namn@a...
other locations to ........................ visual@i...
Coming soon: Part III, Recording magnitudes
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Reporting on the Leonids - PART III
===================================
In this third of my messages about Leonid reporting, I'd
like to encourage you to note magnitude estimates for the
meteors. One of the key parameters in a meteoroid stream
is the mass index which tells how frequent particle masses
are in the stream. For the observer, this mass index turns
into a certain magnitude distribution of the meteors. When
enough mangnitudes are available, the observed distribu-
tion can be converted into particle distributions in
space.
Magnitudes can be estimated without decimals. Examples
for comparison are
Jupiter -2
Saturn 0
Aldebaran +1
Ori belt stars +2
beta CMi +3 the little one NW of Procyon
the four stars of Leo's "head" starting from its body have
gamma Leo +2.5
zeta Leo +3
mu Leo +4
espilon Leo +3
When Leonid activity goes above several meteors a minute,
comparisons will not be possible for each meteor. A good
feeling for the magnitude must be sufficient. The exciting
show may lead to overestimates of the magnitudes. It's wise
to check your scale occasionally with stars. An "inflation"
of magnitudes can be very disadvantageous for the analysis.
The following report gives an example of an observation
with magnitude estimates:
==================
Observer: Tom KING
Place: Huntington, NY (Lat 40.8 N, long 73.4 W)
Time: 9:45-10:46, 19 Nov 2002 UT. [UNIVERSAL TIME = EST+5]
Effective time: 100% (no time lost to looking away or breaks)
Limiting mag.: +5.0 [measured by counting stars]
Field obstructions: none.
Direction faced: Taurus
--
ONE MINUTE COUNTS STARTING 09:45 UT
TIME -6 -5 -4 -3 -2 -1 0 +1 +2 +3 +4 +5 +6 LEO non-LEO
09:45 - - - - 1 1 - 2 8 7 4 - - 23 0
09:46 - - - - - - 2 2 4 6 2 1 - 17 0
09:47 - - 1 - - - 1 3 4 4 4 1 - 18 1
(10%
cloud)
09:48 - - - - 1 - - 3 5 4 2 - - 15 0
(30%
cloud)
09:49 BREAK
09:55 - - - - 1 - 3 1 5 5 3 - - 18 0
09:56 - - 1 - - - - 3 10 9 1 - - 24 1
09:57 - - - 2 - 2 1 3 4 6 3 1 - 22 0
...
Non-LEO all night:
-6 -5 -4 -3 -2 -1 0 +1 +2 +3 +4 +5 +6 tott
Non-LEO - - - - - - 1 - 2 - - - - 2
==================
If the columns of these tables show up mis-aligned, your viewer
for e-mail messages uses a text font with variable character
width. This means, if you _type_ a report, it may also look
mis-aligned with other viewer's fonts. The best thing to do
is to switch your message windows to a monospaced font, e.g.
Courier under Windows.
Activity may become so high that magnitude estimates are no
longer accurate. My own experience is that beyond 20 meteors
per minute, magnitudes tend to be random numbers. Nevertheless,
try to log magnitudes as long as possible. The numbers in the
analysis will be large enough that you do not have to bother
about a few rubbish numbers you recorded. Only if you notice
that you actually lose meteors due to thinking about magnitudes,
stop logging the brightness.
If you have not seen a Leonid storm yet, you may ask "20 meteors
per minute is 1 in 3 seconds and isn't all that dramatic". But
meteors appear at statistical randomness; there seconds in which
you see 4 and seconds in which you see none. This makes life so
difficult ... and enhances the impressiveness of the event!
Send data from...
-----------------
North America to .......................... namn@a...
other locations to ........................ visual@i...
Coming soon: Part IV, Recording all showers
Best wishes,
Rainer Arlt
(
geocities.com/sarmvali)