Hi folks,

Masaki Kouda mentioned problems with two double stars: Mizar and
Albireo. In both cases, the problem is similar. For Mizar, the
Fifth (and Sixth) Catalog of Orbits of Visual Binary Stars gives an
orbit of a very close pair, orbiting with a period of under a month.
This _is_ a real pair; it just ignores the companion star most people
would expect to see (which is also a close double, I think, making
Albireo a "double double". Though you would need quite a scope to
split both pairs.)

Anyway, with the data available to it, Guide ought to split the
brighter component into a pair about .01" apart, leaving the other
component alone, resulting in three stars. (Instead, it thinks the
"other component" should be moved to be .01" from the brighter
component.) I've just revised it to do this, though you have to
zoom in _very_ far to split the brighter component at all.

The catalog also notes that the brighter star in Albireo is also
a close double, with a period of about 97 years. In this case, Guide
gets it right: the brighter star is split into a close binary, and the
other star is left "as is". (The difference is due to the Hipparcos
numbering system, and is a long and ugly story.)

About isophote contrast/brightness: it occurred to me recently to
attempt controlling these much as contrast/brightness are done for
planets and images. You right-click on a planet or image, then use
Alt-arrow keys (or toolbar buttons) to adjust contrast. The same could
apply for isophotes.

In the meantime,

http://www.projectpluto.com/mar_fmt.htm#isophotes

gives some information about how to adjust contrast. In brief, edit
STARTUP.MAR and look for this line:

48 outlined 1 1 31 164 0
A B C D E

Numbers 'C' and 'D' could be changed to, say, 10 and 80 to get much
fainter isophotes.

Incidentally, to shut off the Milky Way but not nebula isophotes,
right-click on a Milky Way isophote, then "display", then set it to
be shown at fields of view from (say) 1000 to 1001 degrees. Graceless,
I realize... but it _will_ cause the Milky Way not to be shown, without
affecting nebula isophotes.

About "realistic", star-like planets: this could also be said for
asteroids, artificial satellites, and maybe even comets. I tried to
do this about a year or so ago... it occurs to me that it may not be
so difficult now, due to some changes in how the code is structured.
I'll give it another look.

-- Bill