Hi Ben,

An 8 MByte UCAC-2 file might indeed slow things down.
(You can check by clicking on a UCAC-2 star, then on
Display, then shut off the dataset. If it suddenly
zips along more briskly, you know UCAC-2 was a
bottleneck. I'd recommend doing this _first_... no
point in going to lots of effort, only to find out
that something else was causing the slowdown!)

There are a couple of approaches you could take.
One would be to get the "original" UCAC-2, in its
binary form, and set up Guide to do that. No more
downloading needed; you just zoom in and UCAC-2
stars appear as desired:

http://www.projectpluto.com/update8c.htm#ucac2_display

Getting the data is a little tricky. You can download
the entire 1.8 GBytes, or you can e-mail me to be put
on a distribution list:

http://www.projectpluto.com/a2_pass.htm

The idea works as follows: I've sent out DVDs
containing the complete UCAC-2 and A2.0, on two disks.
People receive them, copy them, and then I ask them
to mail them to the next person who is interested.

No money changes hands. But you do have to be
willing to pass your copy on to the next person.

Another approach is the one mentioned by John
Greaves: if the 'u2.dat' file containing downloaded
UCAC-2 data is sorted in RA or dec, and Guide happens
to know about that, then display can be a _lot_
faster. Instead of reading that entire 8 MByte
file, Guide can say: "The area on screen extends
from RA=4h20m to RA=4m23m. Let's jump ahead in the
file until we find an entry at the lower RA, and
display stars until we reach the upper RA limit,
and skip everything else in the file."

John's recommended method is a bit involved, but
it _will_ make things faster. And there's no really
straightforward way to chop out particular areas from
u2.dat, or to remove duplicates.

One final possibility: if you've been downloading
bits of UCAC-2 for a while, and are pretty sure that
the stuff from long ago isn't really wanted any more,
you can edit the file, delete the first half of it
(or similar fraction), and save it. The entries in
'u2.dat' are saved in the order in which they were
downloaded, oldest data first, most recent last.

-- Bill