Hi Mike,

That 'C/2010 A3' suggests comet elements that haven't been updated for
a while. Comets start out with a C/ designation; those that turn out to
be periodic are then renamed to P/.

I don't know exactly what went wrong here. It could be that at the time
you got the data, magnitude parameters weren't determined for this object.
In that case, you'd have to turn comets On. You would then find, when
you clicked on the object, that no magnitude would be displayed.

Comets have been an endless source of frustration, for people using Guide
and for me as somebody trying to get the program to handle them correctly.
The official nomenclature can make it a little hard for Guide to figure out
that, for example, C/2008 X1, P/2008 X1, 211P, C/2003 F6, P/Hill,
and P/Hill 2 all refer to the same object.

Anyway. I'd suggest that you _first_ e-mail me the file 'comets.dat'
from your Guide folder, simply because I'd like to know what went wrong
here. _Then_, I'd recommend that you download

http://www.projectpluto.com/comets.dat

to replace your current copy.

This comet list is based almost entirely on a set of orbital elements
compiled by Patrick Rocher, of the IMCCE in France. This provides a very
nice way of evading a lot of the limitations of the MPC dataset, and in
the future, it'll probably be Guide's preferred way of getting orbital
elements.

The only drawback to Rocher's dataset is that it sometimes lags the MPC
site by a few days. To get around this, I'll probably retain the ability
to use MPC comet elements, but they will only be used if they're absent
in the Rocher data. (The 'comets.dat' on my Web site is up-to-date as of
today.)

-- Bill