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(meteorobs) Re: Geminids vs Antihelions



Robert and All,

You seem under the impression that antihelion meteors only appear near
the ecliptic. Actually, they can appear in any portion of the sky. The
radiant is located precisely on the ecliptic. 

On the night of the Geminid max (Dec. 13/14) the antihelion radiant is
located near the star Mu Geminorum in western Gemini. The Geminid
radiant will be close to Castor that night. This is in the eastern
portion of the constellation. The diameter of the antihelion radiant is
at least 20 degrees so there is some overlap. Since both radiants are
fairly close in the sky their velocities are similar. The only way to
tell them apart would be path direction. This will not work for meteors
moving due east or west as tracing their paths backwards would intersect
both radiants. But those traveling north or south will either line up
with one or the other. So if you see a meteor than appears to come from
an area just west of Castor then odds are it belongs to the antihelion
radiant. 

A great majority of the activity on December 13/14 will be true Geminids
so if you are seeing more than 5% of the overall activity as antihelions
then you are most likely classifying Geminids as antihelions.

I hope this helps!

Bob Lunsford



Robert Gardner wrote:
> 
> I just spent an hour between 12:00 pm and 1:00 am PST in my backyard
> reviewing the LM polygons under a terrible urban sky of 3.0 LM
> everywhere except in the vicinity of Gemini which was an amazing 3.8 for
> my backyard.  I saw one dim fast meteor in Gemini which I thought might
> be an antihelion since it was so near the ecliptic.  Later examination
> of my planisphere convinced me that it was not.  However the antihelion
> radiant is in Gemini and moving East and I think it will be at 6h +23m
> on the 13 th of December near mu and eta Geminorum.  For me there is
> some danger of confusing them with Geminids.  As I recal the Geminids
> are medium speed meteors.  What is the speed of the antihelions?  What
> is the approximate size of the antihelion radiant?
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