I've tracked down and fixed the background problem.
Still no ideas on the "disappearing moon" bug, nor on why
asking for A2.0 data might result in getting an "open file" dialog.
Again, if anyone spots something that might be a clue ("Guide
misbehaves when I do _this_, but not _that_"), I'd like to know
about it.
Dario, to have Guide use a JPL DE ephemeris, you have to
add a line to 'guide.dat' pointing to the file. For example,
JPL_EPH=c:\jpl\unix.406
(Those wondering what the heck JPL DE ephemerides are
may want to read
http://www.projectpluto.com/jpl_eph.htm .
Basically, they are the "raw, original" ephemerides on which
most other ephemeris theories, such as VSOP, PS-1996,
and ELP, are based.)
Use of this JPL_EPH= line will cause Guide to get ephemerides
for all nine planets and the Moon from that file. Note that if you've
installed the JPL ephemerides from the second Guide CD-ROM,
you can just use
JPL_EPH=jpl_eph\sub_de.406
This has actually been in place for some months. I didn't
document it, because I planned on adding a more user-friendly
way of accessing it, and on having Guide automatically "find"
the above DE file if no other was specified, and on having
"more info" tell you if a position came from VSOP-87, or the
"short form" VSOP-87 used for low-precision computations,
or from PS-1996, or from ELP-82, or from a given DE. But
it may be a while before I can add all these wonders... in the
meantime, use of the above JPL_EPH line will at least get
things going for you.
A few important notes:
* Most programs have concern about the "byte order" of the
JPL ephemeris files. Guide doesn't care what the byte order is;
it handles either order correctly. Thus, you can use the JPL
DE files provided on the Willmann-Bell CDs, and virtually all
of the DE files available for download from the Internet.
* Guide will handle DE-200, DE-202, and DE-4xx ephemerides.
* If you go outside the time span handled by the JPL ephemeris
file you're using, Guide just falls back on its "usual" code.
* The various DE versions assume different secular accelerations.
Guide doesn't play around with this (nor should it); it just uses
the positions provided straight from the DE files.
Guess I'll have to cut-and-paste some chunks of this for recycling
on the Web site...
-- Bill