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Re: (meteorobs) the radiant
Tom Enders also asked:
>What will be the coordinates of the radiant on Monday and Tuesday evening.
>I understand the radiant does move slightly from night to night. Are the
>coordinates also a function of the latitude of the observer to any extent
>that might be measurable?
Tom, I'd suggest NOT knowing exactly where the Geminid radiant is (or at least
not telling anyone who plans to plot)... The reason is of course to avoid bias.
Also, keep in mind that your friend should measure how LONG he takes to make
each plot (a stopwatch is handy for this), so that he can subtract it as "dead
time" from his observations. Lastly, note that this "dead time" can really add
up on a major shower's peak night! For that reason, most observers do NOT plot
on these very active nights... But you certainly can give it a try!
As for where the radiant will be the peak nights, I always refer to the IMO Web
site's "Meteor Shower Calendar 1999":
http://www.imodot net/calendar/cal99.html
That source puts the radiant at RA 7:28 Dec +33 on the peak night of 14 Dec
(UT). On the following night, 15 Dec, the radiant is at RA 07:32 Dec +33. And
for the previous night 13 Dec, using interpolation gives RA 07:24 Dec +33.
The radiant position should not be substantially different from one location to
the next - though from one side of the GLOBE to the next, there will obviously
be slight variation due to differing times of observation. Anyway for visual
meteor plotting, the GEM radiant is considered as having diameter a few degrees,
so these small night-to-night drifts aren't critical.
Happy plotting, and thanks for asking these great questions!
Lew
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