Bill,
If you could figure a way to show that, you would have another first
in astronomy software, and I know a whole lot of comet crazies like
myself that would be totally blown away!
Tail orientation of comets is a very difficult thing to get right,
mostly because ... as David Levy says, "Comets are like cats, bith
have tails and both do exactly what THEY want to!"
Thanks Bill, for responding to this topic!
Mark S Deprest

--- In guide-user@yahoogroups.com, Bill J Gray <pluto@p...> wrote:
>
> Hi folks,
>
> Sorry for the long silence! I've come back to find a large
batch of
> e-mails; I should be clearing the backlog in a bit.
>
> Guide just shows the tail pointing away from the sun, which is
> usually a good guess. It's been suggested to me that the ion tail
> usually points away from the sun, but that the dust trail usually
> points along the line of variation. (That is, solar radiation
pressure
> knocks off the dust and pushes it out slightly; that results in
the
> dust grains traveling along the same orbit as the comet, but
gradually
> falling behind it.)
>
> Dunno how much truth there is to this. I'll probably try it
out at
> some point; if it works, Guide could show both the ion tail _and_
the
> dust tail, and probably even a dust tail with the right curve.
>
> -- Bill
>