(meteorobs) Size of radiants.

[Roberto G.]

From: "Rainer Arlt" <rarlt at aip.de>
To: "Global Meteor Observing Forum" <meteorobs at meteorobs.org>
Sent: Monday, August 08, 2005 8:35 AM
Subject: Re: (meteorobs) Size of radiants.

> > Thank you Marco, Roberto and Al for your replies. Actually you answered
> > the question as I asked it, however I asked the wrong question. What I
> > had assumed was that the radiant is not a well defined point but is a
> > circle or ellipse from which the overwhelming majority of the meteors of
> > a particular shower radiate. I intended to ask the question of how large
> > is that circle. I have since assumed that ten degrees would be too large
> > for such a circle, but I would still like to propose the question, how
> > large is are radiants in general?
>
> There are two answers to this question: One is the physical radiant
> size resulting from precise video or photographic records. They
> are between 1-2 degrees for 'normal' showers like the Perseids.
>
> The other radiant size is the one, a visual observer has to assume
> when discriminating shower members. Because of the natural errors
> of the visual method, this size has to be larger. If you plot
> the meteors seen in a star chart, you will see that you cannot
> get these meteors converge in a 1-degree circle. This is why
> something like 10+ deg has to be assumed. For meteors farther
> from the radiant, larger sizes (better term 'larger tolerance')
> has to be adopted.
>
> The ecliptical showers have a larger variety in orbital elements
> and produce larger physical radiant sizes. These add to the
> 'torelance' which has to be adopted.
>
> Hope this helps, best wishes,
> Rainer

This it's the perfect answer! There is for the same shower
a fisical and real size that it's 1-2° and a size by human eyes
that in general it's 5° but for some showers as Taurids
can to be until 10° x 15° (and remember that many time the
radiant it's tween) and during some meteor storms this radiant
can to see biggest (Dragonids and June Bootids [this occur only
showers with low speed?]).
Roberto Gorelli