[guide-user] Ax.0 mags, occultations, etc.

Bill J. Gray Dec 27, 1999

Hi folks,

Well, now... all sorts of things have been going on here in my absence.
This will be a long e-mail.

The list of "occultations visible from Japan" reminds me that I will
have to provide a better way to add such lists. I have some ideas as
to how to do this, and the next update for Guide will make it easy to
use this and future lists.

Andrea, regarding Charon: as you've probably seen, not much has been
done to improve this lately. I did post some minor improvements over the
last week (listed on the Web site), but that's about all. For blinking,
the great need is to totally throw out the current 'blink' code in Charon
and start from the beginning. I just haven't had time to do that yet.

I've taken one step that will, I hope, improve progress on Charon:
I'm working toward making it an open-source project. All the C/C++ source
code for Charon is now available. Some people have expressed an interest
in porting Charon to Linux and some Unix-like OSes (no comments on Windows
yet, though.)

Regarding the different sizes of 'printed' vs. 'on-screen' stars: the
difference is roughly 1.5 magnitudes. So you _can_, just before printing,
hit '+' three times. In general, I don't recommend this; the higher
resolution of a printer makes it a better idea to use smaller stars on the
printer than you would on-screen.

If you set a 'line of variation' of, say, one day, Guide will show
lines connecting where each object would be if it were one day "ahead"
in its orbit, to where it would be if it were one day "behind" in its
orbit. Almost always, an asteroid or comet orbit is well-determined in
shape and location; the uncertainty involves where the object would be
along that orbit.

As you mention, the Lowell ASTORB database gives the uncertainty in
arcseconds instead. It would be ideal if Guide could do this, too, but
it would require information it does not have. The uncertainty varies in
a complex way over time, and ASTORB doesn't give enough data to figure
that out.

"...3 We think that it should be more correct to show numbered minor
planets with number and not with name." Errrmmmm... this should be quite
possible. Right-click on a minor planet; then on "Display"; then on
"Options..."; then on either "Label by Number" or "Number, provisional
designation".

Jan, regarding the difference between GSC and Ax.0 magnitudes: this
is indeed an annoying problem, and there is very little that can be
done about it right now. The difficulty is that neither GSC nor Ax.0
magnitudes are very good, and in some areas, they disagree horribly.

One of my strange "research" projects involves recalibrating the
magnitudes in GSC. I know that some of the folks at USNO hope to do
the same thing for A2.0. This will make things at least a little
less terrible.

-- Bill