Hi folks,

BUG FIXES:

A few messages back, Bernd Brinkmann mentioned seeing odd lines in
the CCD frame and crashes when loading marks. I eventually found out
that the CCD frame is drawn oddly if, on the previous "redraw", a
comet was shown on-screen _and_ satellites were turned off. And if the
CCD frame was drawn oddly, loading a new bug caused Guide to lock up.
This was a weird bug.

I still don't really understand why this bug happened, but I'm pretty
sure I've fixed it. I just put new update files on the Web site that
should repair the errors.

TYCHO-2 DISPLAY:

Mark Elowitz asked about Tycho-2 display in Guide 7, using the
Tycho-2 disk. Yes, you could do that using a .TDF file. One slight
difficulty is that the file is sorted by GSC identifier, and not RA.
This means that Guide would have to read through the entire file for
each redraw, and it's a 500 MByte monster. Non-programmers may wish
to skip the following:

The "fix" to this would probably be to have a utility to extract a
desired RA/dec rectangle of data from the file, and have Guide show
that instead. This utility would take the RA/dec rectangle data,
figure out which GSC tiles are involved in that area, and extract
them from the catalog. If you want to do this, the Charon C/C++
source code, described and available here:

http://www.projectpluto.com/source.htm#charon

has certain components you may find useful (actually, they'll
do 90% of the job for you). In particular, take a look in the
grab_tycho2_data( ) function in 'grab_gsc.cpp'; it was added specifically
to let Charon do Tycho-2 based astrometry.

You'll also need the code to figure out which GSC tiles cover a given
area; that's in 'regions3.cpp'. It should be a straightforward job...
and the resulting utility would be useful to a lot of people, I think.
(Unfortunately, I don't have time to tackle it right now.)

-- Bill