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Re: (meteorobs) Geminids from China (Dec. 14/15 ZHUJI)
Jin>>>>However, I did note many bright meteors near the west horizon with slow and short
trails,
'like water drops' when I observed the Leonids last year...
...a beautiful description which matches my experience with the Geminids this
year! I did not get this effect as much with the Leonids due to slower rates this year
and less horizon last year (trees). But shouldn't the angular speed of a meteor appear
to slow down as it recedes from the viewer, much as a foreshortened, near-radiant meteor
(just in reverse)?
Jin>>>>(a) a meteor should always be very short (trail) when it is very near its
radiant. Its trail will appear longer when it is far from the radiant. And it should be
very long when it is seen very far from the radiant.
What if a meteoroid just doesn't ignite until it's far from the radiant,
then flares up only very briefly before going out? Couldn't such a meteor appear as a
"water drop" on the horizon? As you can tell, Jin, I am still struggling with this!
Good fortune in all your observations -- maybe you and I both can catch a strong shower
next year with many "meteor drops" for our study!
Kim
Jin Zhu wrote:
> Kim,
>
> > Let me guess, Jin, that many of these meteors you are describing were at or
> > near the horizon...? My (limited) understanding
> > is that (a) a meteor can never have too short a trail to be associated with its
> > shower (but can be too long) and (b) a meteor moving from overhead down to the
> > horizon will appear to slow (and dim) somewhat near the horizon. I had exactly
> > the same experience during the Geminids. I saw MANY meteors with short path
> > lengths near the horizon moving at, say, a speed of two (slow) but I knew that
> > most likely they were Geminids because they were traceable back to the radiant
> > and the Geminids were at near-peak intensity. So given your other descriptions, I
> > would say it's safe to assume that many of your sporadics were Geminids. It would
> > be good to have an experienced observer give us both his/her slant on this.
>
> For my understanding from books and postings here, the two points are like:
>
> (a) a meteor should always be very short (trail) when it is very near its
> radiant. Its trail will appear longer when it is far from the radiant.
> And it should be very long when it is seen very far from the radiant.
>
> (b) a meteor appears slower when it is observed near the radiant, but faster
> when far from the radiant.
>
> So a meteor far from radiant (say, more than 100 degrees far) should always
> be long in trail and not slower (than its average speed). (theoratically)
>
> However, I did note from my observation that meteors near horizon appear
> to be short ones, except those extremely long ones with almost horizontal
> motion. They were only small part of such horizontal ones in my Geminids
> observation this year for my f.o.v. was almost the zenith. However, I did
> note many bright meteors near the west horizon with slow and short trails,
> 'like water drops' when I observed the Leonids last year during the first
> maximum. I included them as LEOs at the ealier part of my observation but
> then I remembered the above theory and later assigned them to SPOs. They
> did appear at least coinciding in time with the Leonids maximum. I finally
> supposed (not in my report where all non-LEOs were SPOs) that they might
> be some unusual NTA outburst during the LEO maximum - the Leonids
> radiant was low at east at that time, and TAU was about in middle of
> LEO and my west horizon... Except my previous comment that there might be
> some non-GEMs including in GEM reports, I also felt that there were
> some NTAs were regarded as LEOs in previous Leonids reports (I mean those
> received by IMO).
>
> Anyway, I myself is also a new observer and I still need more observations
> to understand all those things together with other observers.
>
> With best regards, Jin
>
> ========================================================================
> Jin Zhu | Tel.: +86-10-62759888, 62756612 (O)
> Beijing Astronomical Observatory | +86-10-62579689 (H)
> Chinese Academy of Sciences | +86-314-5054767 (Schmidt dome)
> P. R. China | Fax : +86-10-62765031 or 64888731
> ------------------------------------------------------------------------
> email: zj@bac.pkudot edu.cn or jinzhu@sun.ihep.ac.cn
> WWW Home Page: http://vega.bac.pkudot edu.cn/~zj
> Pager: zhu_jin@263dot net (only Sub. line) OR +86-10-64256688 PIN 82333
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