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(meteorobs) After the Leonids
Dear meteor observers,
After the maxima of the Leonid meteor shower, the number
of reports being submitted to the Visual Commission of
the IMO is now ceasing gradually. I am trying to compile
a complete set of world-wide data, but need another
week or two to provide the actual activity graphs.
It's a pleasure for me to see all the enthusiasm of obser-
vers contributing to the Leonid picture of 2000. I would
like to thank all the observers for their efforts, in
particular those whom I have not written as their reports
were taken from the meteorobs mailing list.
A number of things could be improved to make it easier
to cope with the flow of data:
- The DATE: In excitement about the past night and still
being tired, many observers forgot to note the date of
their observation in the report.
- FILE FORMATS: Whenever messages are sent by email, they
should be readable independently of the computer of the
recipient. Files produced by Microsoft Word or Excel are
not acceptable, because they do not only require the
recipient to have a PC, he also has to have the exact
version of these programmes. I am urgently asking all
observers to be careful about this problem. (If you are
unsure what to do, look into the "Start" menu of Windows
and choose the "Programs / Accessories / Notepad" editor.)
FORMATTING magnitude distributions. These are often
completely destroyed by variable character widths. I
suggest to use either of the following styles:
Shw -6 -5 -4 -3 -2 -1 0 +1 +2 +3 +4 +5 +6 tot
LEO 0 0 0 1 0 1 2 3 2 5 1 1 0 16
or
LEO -3(1) -2(0) -1(1) 0(2) +1(3) +2(2) +3(5) +4(1) +5(1)
If my first version does not look nice in your mail programme,
choose the second version.
- GROUP WATCHES: In several cases, I received a report
with more than one observer name. The standard measure
for meteor activity -- the ZHR -- refers to a single-
observer count. Observers watching in a group should be
be careful to take their INDIVIDUAL NOTES. No doubly
sighted meteors need to be subtracted. The meteor count
is a data point in a statistical sample of observations
having a natural scatter.
Consequently, the magnitude estimates for meteors as well
as the limiting magnitude should be noted individuallyi,
too.
The argument "We have to cover the entire sky" does not
hold, if you look at the atmospheric volume being monitored.
A field of view high in the sky has a relatively well
defined air volume. If a group wants to cover the "entire
sky" any smallest variation in their horizon is a huge
difference of atmospheric volume being looked through.
The volume, whence the resulting quantities, are essen-
tially undefined when you look down to the horizon.
- LIMITING MAGNITUDE: The limitations of the IMO star-count
areas became obvious for poor conditions. Large steps
between star counts lead to inaccurate LM estimates.
The four-sided outline of Orion may help; here's a list
of star counts versus LM for the area alpha-gamma-beta-
kappa Ori:
# LM # LM
13 4.12 31 5.30
15 4.23 34 5.36
17 4.34 35 5.69
18 4.54 36 5.76
19 4.61 38 5.80
21 4.70 39 5.91
23 4.79 46 5.98
24 4.84 47 6.03
26 4.90 49 6.10
28 5.07 50 6.15
29 5.23
- CLOUD COVER: The cloud cover percentage refers to the
field of view, which has a diameter of roughly 100 degrees.
I inquired a few times to make sure the onbserver used
the field of view for reference, but there were no errors
on that. Just wanted to remind you about this fact here.
Clouds appearing at the edge of the field of view have
less disturbing effect than in the middle, since the pro-
bability to detect a meteor is lower at the edge anyway.
Be careful not to exaggerate the influence of clouds.
I would also like to encourage people to take part in the
utilization of data in the Visual Meteor Database. The
workload of input should be shared. Suitable prerequisits
will be a fair knowledge of computers, best are experiences
with dBase databases. Please consider your capabilities in
this respect and let me know.
With best wishes, Rainer
--
Rainer Arlt -- Astrophysikalisches Institut Potsdam -- www.aipdot de
Visual Commission - International Meteor Organization -- www.imodot net
rarlt@aipdot de -- phone: +49-331-7499-533 -- fax: +49-331-7499-526
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