I'd recommend downloading the following file to your Guide folder:
This will replace your comet file with a "current" one. It will also fix certain
problems inherent in the usual scheme of getting updates from MPC. For example,
if you don't get updates often enough, certain comets can be completely missed
because the updates only contain "currently observable comets"; if you last
got comets in March and it's now July, then you'll get no data for comets
that were observable only in May.
Also, comets that get permanent designations can show up twice in Guide.
As an example, the comet P/2008 R1 recently got the permanent designation
259P. Guide can't tell that these are one and the same, and will show
two comets (assuming you've downloaded, at one time or another, data for
All this has been a real annoyance over the years. I do have some thoughts
for getting around all of it, but it'll be tough to do.
Anyway. The above file has been cleaned up to contain the most current
designations, with no Doppelgangers, and has been rendered complete using
the IMCCE comet list from Patrick Rocher (which shows all comets since about
1995, without worrying about "currentness").