IMO: Reporting on the Leonids - PART II

by the IMO, From: meteors

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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

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.

Observations should be sent to, or North American observers, and to, or all other observers. Your reports then enter the global analysis of the Leonid meteor shower.