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Re: (meteorobs) further suggestion for fireball measurements


Quoting YoungBob2@aol.com:

> In a message dated 7/24/2001 3:20:53 PM Eastern Daylight Time, 
> marco.langbroek@wanadoo.nl writes:
> 
> << 
>  3) Also record whether the fireball fell off to the left or right.
>   >>
> 
> Marco:
> 
> Thanks for the additional tips.  What exactly do you mean by
> fell off to left or right, the falling off of small debris?
> 
> Bob Young

Hi Bob,

I mean with that: whether the fireball was moving from left to right ("fall off 
to the right") or vice versa. In the method I refered to, the measured angle 
for an observer will get a + or - sign in front of it depending on whether the 
fireball fell off to the right or left. For a full description of the method, 
see the paper in Astron. Astroph. I quoted.

As an additional clearification of my suggestion: what I thus suggest is 
recording (in addition to the more common techniques of measuring altitude and 
azimuth of begin- and endpoint of the fireball) for each location the apparent 
angle of fall with respect to the vertical. This either connected to azimuth 
and altitude measurements of the endpoint; or the azimuth of the crossing point 
of the prolonged apparent fireball path with the horizon (preferred, because 
then follow up calculations are less complex). With this method, and 
independant of trajectory reconstructions from altitudes and directions of 
sightings, it is possible to derive the azimuth and altitude of the radiant of 
the fireball with (with a good set of data) an accuracy possible to about 10 
degrees. Measurements are, as rightly indicated by Norman, most reliable for 
sightings near the horizon.

What you basically do with the data (see the A&A reference) is make a diagram 
of angle against azimuth (with falling off left or right indicated by a + or - 
sign in front of the angle). That will yield a sinoid distribution line of 
datapoints. To this, you match a sinoid line of the theoretical relation of 
angle against azimuth calculated for several possible radiant positions. 
Eventually, there will be one that fits data best.

- Marco Langbroek




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