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Re: (meteorobs) Very Fast Sporadics (was Re: Internet Message)



In a message dated 98-09-15 15:14:58 EDT, you write:

Lew<< 
 But I think George generally only considers a meteor "Very Fast" (a "5" on
his 
 and NAMN's speed scale) when it is travelling at, say, Perseid speed or
better, 
 to use a convenient baseline... Is that fair to say, George?<<

No. The scale is an approximate thing...but I generally consider Very Fast
meteors (a 5 on the speed scale) coming from meteors that have entry
velocities over 50 km/s when they show themselves to appear their fastest.
Perseids are 59 km/s. I show this in my guidebook as well. 
 
 Lew>>And even with the added "boost" of Earth's motion, aren't there pretty
few 
 sporadic meteors that will hit us at better than 59 km/sec? <<

Anything appearing in mid sky and not close to a radiant and has an entry
velocity of 50 km/s will appear to me as Very Fast. Generally after midnight
hours I will see a pretty significant number of meteors appearing this way. To
me they look pretty much like a streak and I generally don't see the meteor's
head. If I'm able to dwell on the meteor's head and it appears still fast, I
generally will drop down to 4 on the speed scale and simply call it Fast. 

Lew>>Anyway, I know from 
 the little observing *I* have the chance to do that I very rarely see
anything 
 I classify as a "5" on George's scale, unless a Very Fast shower (ETA, PER, 
 ORI, LEO, etc.) happens to be active... (In fact, I tend to log even PERseids
 as "4", and only a rare long one as "5".)<<

Like I said...I get a fairly significant number of sporadic's doing 5's mostly
after midnight. Perseids I usually log as 5. The rare long one that occurs
when the radiant is just below the horizon I usually give them a 3. I
recognize this as one of the exceptions where the meteor will appear slower
and go accordingly. Sometimes a Perseid will appear a few degrees from the
radiant and I will log it as doing a 2 or 3 usually. Again recognizing this as
one of the exceptions where a meteor will appear slower. 
George Zay

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