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(meteorobs) Re: NM South Delta Aquarid ZHR



"nmcleod@peganet.com" wrote:

> Kim also points out the difficulty of classifying July meteors.  This >is indeed the roughest, most complex period of the year with so many >radiants active.  It took me about 5 years to get comfortable with it. >Speed alone becomes meaningless for the shortest meteors. I take >duration into account as well to get some idea as to how fast a meteor >is going.  Last week I saw a meteor go only 1/6 degree in 0.3 second, >so that is a fast one. Converting that to degrees/second gives 5/9 of a >degree per second which would be very slow.  This meteor was obviously >not slow.  It looked distinctly different from a point satellite flash > also.
> 
Norman,

1/6th of a degree? You must have micrometer eyes! This very short meteor
WAS traveling slowly if your estimates are correct. It's the duration
that was quick making it appear as a swift meteor. 

I will be the first to admit that I also had trouble relating speed and
duration's. During the 1994 Alpha Aurigid outburst I was seeing meteors
lasting several seconds. I was having a difficult time assigning them a
numeric velocity. I KNEW that the AUR's were a swift shower but I found
difficulty in assigning meteors a speed of 5 when they lasted several
seconds. Heck, swift meteors last .2 to .4 of a second, not several
seconds! I was emphasizing duration when I should have realized that a
meteor traveling 75 degrees in 3 seconds is indeed swift (25
degrees/second) but it "looks" slow.

This led to me abandonment of the numeric scale in favor of estimating
both length and duration which produces an estimate of the angular
velocity. I was not certain though just how accurate my duration
estimates were so after several years of this I have also added radiant
distance and altitude for shower meteors to achieve a better accuracy of
duration. If I can obtain a good estimate of the length of each shower
meteor then I can use radiant distance and altitude to obtain the
duration and angular velocity.

This is definitely not a project for newbies but just a mid course
correction for me on that journey to more accurate visual meteor data.

Clear Skies!

Bob
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