Hi folks,
Many thanks for the kind words about (15964) Billgray and the Saturn
satellite IAUC. The asteroid naming did come as a total surprise to me,
until I got the e-mail from Jim Roe telling me about it. (Jim and I
have been swapping e-mails, mostly about Charon, for some years now.
We finally met this spring at the Minor Planet Workshop, in New York.)
Naturally, I immediately spent a bit of time looking up the particulars
of this object (size, orbital elements, etc... it's in the Hungaria
group of asteroids, with a high inclination and an orbit on the inner
edge of the main belt between Mars and Jupiter; see
http://www.projectpluto.com/mp_group.htm#hungarias
for more than you would ever want to know about asteroid groups and
families.)
The Saturn satellites have been giving me (and others) an
interesting mathematical and observational time. You normally think of
orbit determination as a cut-and-dried exercise, but doing it for a
satellite of another planet is a different matter. I've made several
changes to my Find_Orb software in efforts to get better planetary
satellite orbits, and expect to make still more in the coming weeks.
Incidentally, if you're interested in how orbits are determined from
observations, Find_Orb is discussed and downloadable (minus the new
improvements, which aren't quite "user-friendly" yet) at
http://www.projectpluto.com/find_orb.htm
I started out doing planetary satellite orbits about a year ago,
with the three new Uranian satellites (now named Stephano, Prospero,
and Setebos). I asked Brett Gladman, who heads the team that found
these objects, if I could see the astrometry for use in my software.
He sent it, and said he'd like to see any orbits and ephemerides I
came up with, as a check against other results. That astrometry is
now posted on his Web site, and if you'd like to try computing orbits
for these objects (and read about and experiment with some other odd
orbital determination cases), look here:
http://www.projectpluto.com/cassini.htm#uranian
James Ellis mentioned "a new moon of Jupiter that needs refinement".
That would be S/1999 J 1, and it did get some new observations from
Spacewatch on 3 November (which will be reflected in the next update I
post on the Web site). It's about mag 20, and nicely far from the
glare of Jupiter right now. The ephemerides are much better now, but I
think the folks at MPC would be happy to get some more astrometry on it.
(And please send me the astrometry, too!)
Christophe Demeautis, a Guide user in France, tried to image this
object in late September, when it was moving _very_ slowly, at a
stationary point, so he could do a longer exposure. His images didn't
go quite deep enough, but S/1999 J 1 will be moving about 2 arcseconds
an hour in late January, 2001. It would be an excellent time to try
observing it again, and would help the orbit solution quite a bit.
Mark Huss wrote:
> No wonder he can't get Guide 8 finished! ;-)))
Well, yes... getting the software to search for sensible Saturnicentric
orbits took somewhat more effort than I expected. (Though most of it is
past me now; when new observations come in, I can spit out a new orbit
in mere minutes.) On the bright side, you can count on Guide being the
first software to show these new objects. (I could have Guide show
satellites 1, 2, 5, and 6 right now. But the orbital solutions for 3
and 4 are still not very good. In fact, I've got only a very vague idea
as to where those satellites are, and I _hope_ somebody manages to
recover them soon.)
> Seriously, I wonder if Bill ever gets time to look through a
> telescope anymore...
Not much, I'm afraid. But it has more to do with the cardboard tube
on my 13.1" Coulter Dob gradually unravelling, to the point where I've
decided to do a total rebuild. The result will be an immensely better
scope. But I have deliberately set that on the shelf until I get Guide
8 done... the satellites have been enough of a distraction!
-- Bill