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Re: (meteorobs) Re: NM South Delta Aquarid ZHR




malcolm>>If you are plotting meteors to investigate minor showers, then a
reasonable estimate of the speed is important.  Given a precise speed
and position it would define the radiant.  The speed specifies the
distance of the meteor from the radiant, and the position and
orientation define the great circle containing the radiant.  The
intersection is the apparent radiant.<<

In reference to plotting, I think I mentioned speed's  importance  or perhaps 
just implied in another post? At least that's what I had in mind when I 
mentioned if you have a plot, you have something to utilize speed estimates 
and refer to. Whereas when just using the Counting method you don't.  Whether 
you use a speed scale or angular estimates, they both can be used about 
equally when investigating minor showers.Neither method will provide precise 
speeds. They both can provide some hint as to a velocity range that is 
involved for each meteor when either a radiant position is considered or 
suspected.

malcolm>>When you combine lots of observations and sum up the various
probabilities at different locations on the celestial sphere, e.g.
with RADIANT, the radiants will become obvious.  If you don't include
the velocity you may well still see a prominent radiant, but the
signal to noise is greatly reduced and weaker showers are lost.<<

Very true.....both angular velocity estimates and a speed scale can be used 
to relate a particular plot as belonging to a radiant. I have no problem when 
looking at my plots while looking for potential new showers or just making 
judgement calls on shower associations for minor showers using a speed scale.

malcolm>>One disadvantage to a scale over degrees/s is that the normalisation 
to
degrees/s needs to be determined for radiant analyses.  <<

This would be a disadvantage, but a problem that could be worked out at a 
more leisurely pace than while doing the actual gathering process. I've 
talked to Rainer Arlt about this several times in the past. Of course he 
would rather I go to angular velocity estimates predominantly to make his 
work easier, but I think there should be less pressure as possible on the 
observer while gathering data for a plot. The less a person has to mentally 
juggle in their head for each meteor while out in the field, collectively the 
more accurate the plots will probably end up being. A disadvantage while 
determining degrees/second to using a speed scale, is that you have about 2 
or 3 more  active things to think about than you would with just a speed 
scale for the same purposes. You already got at least magnitude and meteor 
trajectory in the sky to keep in your head and the introduction of a couple 
more active things to thought can easily lead to a variety of errors. I think 
everything should be done to make it easier on the gatherer of data where 
possible, especially if nothing significant is gonna change with the final 
analysis.
geozay
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