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re: (meteorobs) Perseids & Radiant Drift

Cathy wrote:
The two of us also had an interesting discussion on radiant drift, but
regarding the Capricornids, not the Perseids.  I mentioned that I thought 
it
would be a neat idea to do up some reference maps showing <lines> for the
radiant positions, with beginning and end dates, and several dates marked 
in
the middle for long drifts.  I realize that all the various meteor 
calendars
list radiant drift, but it is <<much>> easier to visualize and remember
something when you're looking at a star map, instead of just a table of
numbers!! ...  
Wayne unloaded with:
	In fact, the latest edition of the IMO handbook has just such charts!
I also produce for my snail mail readers of Radiant Rising, charts 
containing all active showers during each lunar period (Full moon to Full), 
based on the aforementioned IMO handbook, as well as radiants from other 
sources including Peter Jenniskens paper for the DMS, and Gary Kronk's 
historical listing. Mighty darn crowded in AQR-CAP-SAG-SCO this time of 
year!!!
	In actual fact, when you start plotting all the radiants from the N & 
S delta Aquarids, N & S iota-Aquarids, alpha-Capricornids etc, when they 
are concurrently active, you can truly appreciate the difficult task of 
separating members of these showers. Only the CAP's stand out a little due 
to slightly slower velocities, the rest overlap severely. Purely by visual 
counting, I would suspect only VERY experienced observers (> 50 Hr Teff/Yr),
 would have any chance of accuratly doing this. (Even though I fit in that 
admittedly arbitrary category, I would feel very uncomfortable separating 
them without the benefit of my plots). Hence it is my personal belief that 
beginning/novice observers should only report a generic AQR (for Aquarids), 
but that thought is just simmering. Even with plotting, due to the inherent 
accuracy limitations, it is problematical at best. This is an issue that I 
will soon be addressing in more detail, but other pots on the fire are 
boiling, while this one has only been stewing in my head for a day or two 
(starting when I plotted all those radiants together on one chart!). In 
Radiant Rising, we also include a chart with daily radiant positions (RA 
and Dec) for each active shower, and when doing so extend the official 
start and stop days for those who wish to look for them. (For those who 
have the excel spreadsheet program, I can e-mail you a copy if you wish) 	
However, once again I emphasize, identification of showers when they have 
ZHR's of 2 or less is quite unreliable by <in the field> identification. 
Only plotting, from many people across the globe, or photographic/video 
evidence can statistically prove that activity exists at such a low rate.
	One cannot discount the issue of sporadic pollution (sporadics meeting 
shower identification criteria). For details on the theoretical discussion 
of this issue, I strongly suggest reading the IMO
handbook, or the original articles on which it is based. I don't have the 
reference with me at the moment, but I will have it tomorrow if anyone is 
interested.

Regarding the Perseids:
	Based on the IMO information, projecting the radiant backward in time 
to July 5/6 th (when I also observed), the radiant would be RA 001 degree 
(0 Hr 4 min), Decl + 49.
FWIW, in 1.7 hours of looking for these early Perseids (July 5/6) I saw 
none.
One must be very careful in counting these as Perseids, for if you are 
going to challenge
current theory and observations you must be meticulous in your data 
gathering...but if you can show that you are, then you should report 
whether you see them or not. Just be sure to use accurate radiant positions,
 and carefully apply the shower identification factors. (Radiant size vs 
distance to meteor, meteor velocity vs distance to radiant, etc)
	Many casual observers often do not have the actual radiant in mind, 
since it is so far from Perseus. So just take extreme care in making the 
ID!
	I also observed 0ne JPE (July Pegasid), whose velocity is nearly 
identical to the Perseids..dot be sure the ones you saw do not align with that 
radiant (which was 339d [22 Hr 34 m], +14) since they are easy to confuse.

Just my can of gas on the fire

Wayne Tv
Sweatin' with the meteors, all night long
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