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  tot
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@atmob.org

other locations to ........................ visual@imo.net

Coming soon: Part IV, Recording all showers


Best wishes,
Rainer Arlt


--
Rainer Arlt  --  Astrophysikalisches Institut Potsdam -- www.aip.de
Visual Commission - International Meteor Organization -- www.imo.net
rarlt@aip.de
 --  phone: +49-331-7499-354  --  fax: +49-331-7499-526