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Re: (meteorobs) Re Observations Sth Tau, Orionids, Pup Velids 2nd Oct 1997

In a message dated 97-11-04 11:34:30 EST, you write:

Jim<< 
 This is not a criticism, George, just an opinion:
  From the researcher's point of view, the above method would introduce a
 systematic bias in the data, by having the observer interpret shower
 membership based upon a preconceived notion of what component is most
 active that the time.  <<

I agree.
 
 Jim>>If you believe that the Southern Taurids are more active than the
Northern
 Taurids on the night that you observe, and you interpret questionable
 alignments as Southern Taurids because of this knowledge, then - presto -
 your data will show the Southern Taurids to be the most active:  thus
 proving your preconceived notion.  <<

Also agree.
 
 Jim>>Unfortunately, this is not very accurate or objective, and reduces the
 scientific value of the data.  I think that it would be more objective to
 call such questionalble alignments simply "Taurids" and let it go at that.<<

Also agree...but any researcher who is worth his salt would be aware of the
Taurid alignment problems and automatically group all the Taurids into one
group if he doesn't feel comfortable about shower judgements.  Doing this
later doesn't diminish the value of the overall Taurid report. 

Jim>> I would propose that visual observers exercise extreme care in not
letting
 their own preconceived notions about radiant locations and activity levels
 influence their actual data collection (Upsilon Pegasids, anyone?).  The
 data should objectively point to the actual meteor activity, rather than
 letting "knowledge" of activity influence the data.<<

Agree...but in the case of the Taurids, the problem is for  meteors that
align with two very close radiants and have meteor characteristics nearly
identical. Normally I plot minor shower activity such as the Taurids. I plot
the way I see them...not the way I think they should align. If I plot the way
I think they should align...I think my plots would look like neat "bullseyes"
leading to the radiants? I can assure you that they don't look this neat.
When Rainer extracts the coordinates for each meteor from my plotting charts,
 the opportunity to be re-interpreted as to what they might have been still
exists. When utilizing the Counting method, it's a one shot thing and no
turning back. Unfortunately, the other night was under difficult wind
conditions that made plotting almost impossible (winds at 35 mph). The
Counting method was only used as an alternative because of this. Not all
Taurids will be difficult to determine which radiant they belong too...only
those that are in alignment with the two radiants. Somewhere in the process,
one is going to become aware of radiant locations. This could be out in the
field if one is making judgements then...or at home when one is reviewing the
charts and making judgements later. Irregardless the method used, in both
situations you will have meteors that are in alignment. It becomes a "pay me
now or pay me later" situation...you will still have to the face the dilemma.
The alternative to this problem would be thru photographic means equipped
with a rotating shutter....but would only apply to the very bright
meteors...unless a sensitive video camera is available.
 
 Jim>>I know from personal experience that this is much easier said than
done.  I
 remember one year in particular when I was just learning to plot that my
 Delta Aquarid plots split very nicely into the separate components, with
 small radiant areas -- TOO nicely.  It was a very pretty plotting chart,
 but i had obviously let my foreknowledge of what I expected to see that
 night influence my recording of what I actually did see.  This is a very
 easy trap to fall into.<<

Experience at plotting will reduce these kind of errors...as well as becoming
a mature observer.  Quite often I don't know where a particular radiant is
located at. Though I have been observing quite frequently and usually  do
have a pretty good idea as to where the radiant might be. As for the Delta
Aquarid's, I usually don't plot these during maximum nights...particularly
the S. Delta Aquarids. Meteor activity on these nights are quite
high...usually more than 20/hour. I don't plot with activity over 20/hour. I
revert to the Counting Method...that is I record everything as I would when I
plot...except I don't do the plotting. The Aquarids have a variety of
radiants that can cause problems...particularly for the inexperienced. But
they are no where as problematic as the Taurids. The various Aquarids (North
and South Delta, North and South Iota then add the Capricornids and Piscis
Austrinids) are all in the general area...but still spread out far enough to
note the difference in velocities for some or alignments. There still will be
some that will be difficult to determine....but compared to the Taurids it is
nothing. The Taurids...both North and South are very close...slightly
overlapping. Also their radiants are quite large. For meteors that occurs a
far distance from the radiant, the normal inaccuracy of alignment will easily
make either radiant a likely candidate. Under these conditions or situations,
you can only do the best you can with the knowledge and experience you have
available. 
George Zay