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Re: (meteorobs) Leonid report - narrative - Nov 17/18, Mt. Lemmon, AZ (ATAJU)



On Wed, 28 Nov 2001, Larry Wood wrote:

> I checked using Guide 7 and here in Edmonton (Elev 672 m) on the 18th the
> radiant center rose at  05:27 UT.
> If at 111 km elevation the radiant center would have risen at 03:37 UT.
> 
> Larry Wood

What this is saying is that at 03:37 a Leonid would have had to pass at
ground level on the apparent horizon from 111 km.  Using the ground level
radiant corrected for zenithal attraction (0.7 deg for the Leonids) gives
the time Leonids overhead will be moving horizontally (at perigee).  A Leonid
with perigee towards the azimuth of the radiant can pass overhead if it's
height doesn't become too large as it passes back out into space.  The
several Earth-grazers I saw around Leonid rise certainly looked to have a
slower angular velocity, presumably due to being at much greater heights
and thus much greater distances than average Leonids seen later in the night.

Although a radiant may be given as 5 degrees, this may just be to accommodate
observational errors.  Predictions for dust trails indicate a radiant size
of only a few arcmins at most for specific dust trails, although other dust
trails and background Leonids will certainly make the overall radiant larger.
Preliminary results from a radiant experiment at Siding Spring indicate a
radiant only around 3 arcmins across at ~17:30 UT on Nov 18 based on 10
Leonids.

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