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Re: (meteorobs) Observation 19/07/2003


>* Sagitarrids are "officially" over, but the Antihelion
>radiant remains (or not?), but I don't know what to call
>these meteors, so I'll stick to ANT

If I'm correct, the Antihelion source is somewhere in Capricornus right 
now, and produces activity all year! (In fact its rates are considerably 
higher from +-July til December. See IMO's visual handbook for more 
information and references about this.)

The only guideline I know about the reporting-issue, can be found in 
Mr.Lunsford's wonderful meteor outlooks; quote: "It may make sense to list 
these meteors as antihelions or 'ANT' but a majority of meteor 
organizations prefer that you list them from the constellation in which the 
radiant is currently located or the constellation where the shower reaches 
maximum activity."

The second way is probably the standard procedure to report any higher 
activity coming from a certain area in the sky, not associated with a known 
shower. My guess is that these rates are most likely added to the 
"SPOR"-value right away, when you submit the data to the IMO visual meteor 
database.. However, I see that the vmdb also contains meteors that are 
classified as "DIV" (wich is obviously not a standard shower code). Can 
anybody tell something more about this?

Btw; what if this interferes with actual meteor showers? You could, for 
example, report both alpha-Capricornids and antihelion-meteors as "CAP"? 
(Tho accurate plottings may enable you to distinguish both). The same thing 
happens in August, when the Antihelion-source comes really (really!) close 
to the aquarid-radiants.

I'm sure some people may be disappointed that sporadic sources are not 
treated like 'real' showers in the processing, but they are probably just 
too big (+20°!!), and not observed widely enough to use visual observations 
for reliable statistics. Radio-observations have been used in the past to 
determine the positions, structure and relative rates of the sporadic 
sources (cf. some articles by Jones&Brown in mid-90's), but many questions 
remained. Maybe video-observations can gather accurate trajectories and 
rates?

Kind regards,
Geert


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