IMO: Leonid reports, Part 3
Leonid reports, Part 3More articles in IMO
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 distribution can be converted into particle distributions in space.
Magnitudes can be estimated without decimals. Examples for comparison are:
Ori belt stars +2
beta CMi +3
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
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 firstname.lastname@example.org, all other observers to email@example.com