Lawrence, about isophotes: the contrast/brightness for these isn't
adjusted via an "options..." button (which, as you note, is grayed
out for isophotes.)
Instead, after right-clicking on an isophote, you can use the arrow
keys to adjust brightness and contrast. (Similarly, after right-clicking
on the corner of a DSS image or on a planet, you can use arrow keys
to adjust its brightness/contrast.) The part about isophotes is
described a bit at
http://www.projectpluto.com/update8.htm#isophote_contrast
Kevin, about NGC finding: as you found out, you do have to have
the DSO data loaded before Guide will find an NGC object. That leaves
us with the mystery of why it's crashing. First: does it work properly
with the first Guide CD in the drive, but fail without it? (I've tracked
down and killed a slew of bugs of this ilk, but one more wouldn't
surprise me.) Second, can you send me (via private e-mail) your
'startup.mar' file, so I can replicate your setup?
Roger, about blocking off the horizon: combine Rafael's suggestion
of turning the "ground" white, and Arild's suggestion about the
GROUND_DRAWING=2, and Shawn's suggestion about Alt-N,
and I think you should be all set. (I just tried it; looks to me as
if, in a truly "realistic" mode, Guide should show a white ground
if it's winter at the currently-specified latitude.)
-- Bill