Hi folks,

Some comments on making bitmap files, a bug in display of some
user-added datasets, and some information on spectral classes,
asteroid occultations, and relativistic corrections to orbits...

MAKING BITMAP FILES:

This has been a really nasty problem for a while now. I have
some discussion of it, including some workarounds, at

http://www.projectpluto.com/faq_curr.htm#bmp_failure

I appreciate the comments on it, especially since I still cannot
get the function to fail. It relies on the Windows device drivers,
and the failures depend on which graphics card you have. Also, it
appears that the bitmaps load up just fine in some programs, but not
in others. At present, the only way I can see to get around this
would be to evade use of the Windows drivers, probably by creating
my own "draw graphics to a memory bitmap" functions. (Not necessarily
as ugly a job as you might think, and it would have assorted side
benefits. But it certainly won't happen real soon.)

Bernd's comments on the confused RGB values are particularly
interesting. I know some people have reported complete failure of
the 'make a .BMP' function, on maps of _any_ kind. Others reported
failure to load in one program, but not in others. And so on. The
exact nature of the problem(s) varies from video mode to video mode,
and graphics card to graphics card.

BUG IN DISPLAY OF USER-ADDED DATASETS:

Masaki Kouda pointed out (in a private e-mail) that the Zodiacal
Catalog is displayed improperly in the current (8 September) version.
Objects between dec -10 and +10, and between 0h and 10h in RA, are
not shown.

I'd introduced some new code in this version to suppress display of
"spurious" lines (text in a file that might be, say, header data or
comments, rather than actual object data). That new code was more
clever than the original code, but apparently not clever enough.
Some datasets other than the ZC are probably also afflicted. I'll be
posting a fix to this shortly.

SPECTRAL CLASSES:

Oliver Kloes sent a table for Guide's "Miscellaneous Tables",
titled "Classification of Stellar Spectra", containing information
as to what each spectral class means and examples for each. I really
thought this ought to move into the Help system, and I still think
this would be a good idea... but Oliver sent it a while ago, and I
still have not made this move. So I am posting the file at

http://www.projectpluto.com/spectral.etb

Download this file into your Guide directory, and click on "Tables...
Miscellaneous Tables", and you will see this file listed.

ASTEROID OCCULTATIONS:

Some of you may recall that, a couple of years ago, I maintained
a list of asteroid occultation predictions on my Web site. At the time,
making such predictions was a pretty ugly process on my end, and I
got tired of the time required to maintain that page and dropped it.

Since then, I've made some improvements and can produce updated
predictions based on good astrometry without too much trouble. The
page is at

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

RELATIVISTIC CORRECTIONS TO ORBITS:

Somebody (don't remember who) asked me, a while back, how to
include the effects of relativity when doing orbit computations.
(This usually doesn't matter much; the most famous case where it
_does_ matter is the precession of the orbit of Mercury. The ability
of relativity to account for this, exactly, was one of the key
points that caused relativity to get wide acceptance.)

Anyway, I recently learned that including this effect is much
simpler than I thought, and I wrote a few paragraphs about it:

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

-- Bill