Hi folks,

Catching up regarding Lawrence's "bright asteroids" coming back from
the dead; Martin's issue with asteroids not showing up; Luc's question
about getting rectangular RA/dec grids in cylindrical projections.

RE-EMERGING BRIGHT ASTEROIDS:

Lawrence, my first thought was that perhaps MPC had done something
weird with the MPCORB format. (Every now and then, it's been changed
unexpectedly.) But I got a fresh copy of 'mpcorb.dat', and all worked
Just Fine. So I'm mystified.

Is it possible that you have two installs of Guide on your hard drive,
and only one got updated?

Failing that, I'd suggest deleting the file 'astnames.dat'. This
will force Guide to rebuild MPCORB-related files; it could be there
is some other cached file that hasn't been properly cleaned out.
(Seems unlikely, though; once you got rid of the spuriously bright
2010 DK71, I can't see how it could possibly come back!)

Also: when you click on Help... About Guide, what version date
do you see?

NO ASTEROIDS ON WIN98/DOS:

Martin, you mention running guide8a.exe in Win98. Is there any reason
you aren't running guide8.exe in Win98? Guide8a is the old 16-bit flavor;
it really should only be used when running in Windows 3.1. (I don't
know of anyone who is doing this anymore. Also, be warned that guide8a
has not been updated for many years; the program grew to the point where
I could no longer compile a 16-bit version.)

The DOS version of Guide should work, though. I _have_ been able to
update that, and some people are definitely still using it for the same
reason you probably do: they have a Mel Bartels drive system that works
only in DOS. For this, if you are not using the current DOS version of
the Guide software, I'd suggest upgrading. In particular, if you run
recent Guide Windows software and an older DOS Guide, both in the same
folder, there may be some conflicts. The formats of the 'startup.mar'
files and of some of the temporary asteroid files, for example, won't
match up.

RA/DEC GRIDS IN CYLINDRICAL PROJECTIONS:

Luc, you're right; to give a concrete example, suppose you've
set up RA/dec grids for the epoch J-2700. In this epoch, the RA/dec
grids will converge on Thuban (Alpha Draconis), the pole star of
4700 years ago. But Polaris will still be at the top of the map
(assuming you've set "north up" in the Inversion menu), and if
you go to a cylindrical projection, it will be the areas around
Polaris (and Sigma Octans) that are stretched into lines, much
as the north and south poles are on maps of the earth.

Guide's concept of where the "poles" are should be epoch dependent.
That is, if you set the default epoch to be J-2700, then Thuban
should be at the top of charts, and it should be that in cylindrical
projections, the area around Thuban is stretched out. I've revised
Guide to do this. It has the effect for which I think you were looking:
if Guide's default epoch and the grid epoch are the same, then (in
cylindrical projections) the grid becomes a simple rectangular grid.

I'm not posting this quite yet, because I'll be adding display of
UCAC-4 data (I have a preliminary copy on DVD, and it appears no
format change will be made for "final" UCAC-4). But this fix will
appear the next time I post an update.

-- Bill