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Re: (meteorobs) Re: NM South Delta Aquarid ZHR
bob>>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.<<
Yes, this was one of those special circumstances that you have to take into
consideration since the radiant was along the horizon producing earthgrazers.
Alignment, path length in relation to radiant location and date was used more
for shower association than velocity. It posed no real problem.
bob>> 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.<<
You could have assigned a speed of 3 or even 2 if you liked....just as long
as you recognized what special circumstances were at play. Long meteors
coming from an area near the horizon will produce slower appearing meteors.
No problem.
bob>>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.<<
All this mental exercise with each meteor just for shower association? It's
not needed really. Shower association could be done a lot more efficiently
with less hassle using a numeric scale. It's a waste of time to try to
figure any accurate velocities for a meteor since they won't be anywhere
near as accurate as a camera or other electronic means. For what purpose
other than shower association is visual meteor speed estimates used for? I
can't think of any. However good you get at estimating angular velocity, it
won't be accurate enough to replace the results gained by high tech
equipment. All you need to be is accurate enough to provide for adequate
shower association. You don't need to measure anything or estimate any
durations or do any kind of math in your head....just record the speed
impression you get from Slow to Very Fast and have some rough sense of the
meteor's distance from radiant and know what it means.
GeoZay
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