Hi Denis,
> Can I make a suggestion. At present, I use the alt-j to point
> MPCORB_PATH= to the file I wish to use. Why not make a selector for a
> MPC file the same way a "TLE" file is selected for display. People would
> download from the MPC site the needed files and select the one to
> display when needed. This would avoid changing the name in alt-j mode or
> renaming the file to "mpcorb.dat"
Seems reasonable enough to me. This _would_ mean that if you were
using a "subset" file such as, say, NEA.txt, all you would see would be
NEAs; no way to show main-belters and such without switching back to
MPCORB.DAT. Some who just want to see NEAs would regard this as a feature
rather than a defect, though.
The procedure would have the benefit of being quite "safe". You
wouldn't be trying to mix some objects from NEA.txt with everything
else from MPCORB.DAT or Guide's "built in" asteroids. So it would be
a lot less likely to cause crashes, mis-labelled objects, and so on.
There are also some pretty nice speed benefits from this. At present,
use of MPCORB.DAT can cause Guide to slow down for a few seconds whenever
you change the date far enough from the present, or get a new MPCORB.DAT,
because it has to recompute half a million objects. The "subset" files
are about 50 times (or more) smaller; the time spent to display them
is just about unnoticeable.
I should mention two things of interest to anyone who wants to display
only certain types of asteroids. First, you may want to look at a
program I wrote to extract objects with certain characteristics:
http://www.projectpluto.com/mpcorbx.htm
This lets you select, say, all objects with perihelia less than 1.2
AU, or inclinations greater than 10 degrees, and so forth, to make
your own MPCORB subset. Which, if it's a lot smaller than the "usual"
half-million-object MPCORB, will run a lot faster in Guide.
Secondly... while running Guide, you can reset which asteroids are
shown. See
http://www.projectpluto.com/update7.htm#asteroid_filtering
for details. This doesn't result in much of a speedup, though,
because Guide is still working with those half-million asteroids.
-- Bill