Hi folks,
'CURRENT TIME' BUG:
This one has me utterly baffled. I go into the 'Time Box' dialog,
click on 'current time'... and the time shown is updated to that of the
PC clock. No problem at all. I thought Denis Boucher might have
been setting the current time by hitting the F3 hotkey, but that seems
to work fine, too.
Bob Elliott suggested it actually had something to do with the time
zone dialog; _that_ appears to work correctly, too. But the reports
have been a little short on details as to exactly what steps were taken
to get the bug. If anyone else sees such misbehavior, please let me
know (private e-mail may be a good idea).
LUNAR MOUNTAINS:
I've posted a new PLANETS.ZIP to reflect the 'moved' mountains Niels
Foldager mentioned. Those who don't wish to download that file again
(it's about 580 KBytes) should just edit PLANET10.GAZ, and change lines
6965 and 6966 to read:
-004.05 +26.71 Hadley Mons
-003.56 +25.96 Hadley Delta Mons
Niels wrote: "...compared to Guide7's accuracy regarding the lunar
features in general..." Thank you for the kind words... but I've actually
seen some places (too many places!) where all the names are shifted a bit
relative to the bitmap. I am not sure if the Clementine map is in error,
or if the lunar features (from a USGS site) are in error. It never causes
a problem in understanding which features are which. But it _is_ somewhat
disconcerting.
SATELLITES:
For identifying satellites in Guide, it is _very_ important to have
reasonably current elements... the newer, the better. Using those, I
had no difficulty in identifying the satellite James asked about as the
Compton Gamma Ray Observatory:
Satellite max mag Alt Rise ExitSh EnterSh Set SunA RAz SAz
3 Feb GRO 3.2 38 10:04:40 --:--:-- 10:11:56 10:16:29 -14 287 80
(Times are UT.) The 'rising in the west/setting in the east' was a
strong indicator, but it helps that it went between Aldebaran and M45.
There are a lot of sites with orbital elements, but I usually get fresh
.TLEs from Mike McCants' site:
http://www.fc.net/~mikem/tle.html
Use MCCANTS.TLE, and you should be able to replicate the above.
FILTERING PHAS:
Yesterday, I got a private e-mail from R. Mark Elowitz, stating that:
"...To filter out PHAs perform a boolean search on the following
requirements for such NEOs:
MOID <= 0.05 AU
and
H brighter than OR equal to a value of 22, which simply states
that such asteroids must be larger than about 150 meters.
where H is the objects absolute magnitude parameter."
Determining the MOID is a little unpleasant. Right now, Guide does
not do it at all. The most you can do is to say that, since the earth's
aphelion distance is about 1.03 AU, any object with q > 1.08 _cannot_ be
a PHA. This is a "necessary, but not sufficient, condition."
I _could_ write code to compute MOIDs, and may do it someday out of
intellectual curiosity, but it would really make more sense for Guide
to use the MPC's existing list of PHAs.
James, you're right in thinking that if you determine the points
where an asteroid goes through the ecliptic (ascending and descending
nodes), and these are close to the earth's orbit, you can be sure it's
a PHA. But you can easily have cases where the asteroid crosses the
ecliptic far from our orbit, but then approaches us at another point in
its orbit. So the situation you describe is a "sufficient, but not
necessary, condition." There's really no way of evading the need to do
a lot of math.
DOS GUIDE:
Berthold, you're right... the link was incorrect, and leads to the
updated DOS Guide 6 software! I've fixed this.
I knew DOS Guide users were a vanishing breed; the fact that I've had
the DOS software in the wrong place for over a year, without anyone
remarking on it, confirms this!
-- Bill