E12 doesn't have particularly accurate photometry, but visually on
the screen, this object has a dramatic lightcurve.  Probably over a
magnitude amplitude tonight and similar last night.  Period or half
period is ~~ten minutes, but very rough.  This H=25 object is
also a VI.
Cheers, Rob

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Robert H. McNaught
Uppsala Telescope/Siding Spring Survey
Australian National University
Siding Spring Observatory
Coonabarabran, NSW 2357
Australia

P:  +61 2 6842 6260
F:  +61 2 6842 6240

SSS Webpage: http://msowww.anu.edu.au/~rmn/
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

On Mon, 1 Dec 2008, Robert McNaught wrote:

> E12 doesn't have particularly accurate photometry, but visually on
> the screen, this object has a dramatic lightcurve.  Probably over a
> magnitude amplitude tonight and similar last night.  Period or half
> period is ~~ten minutes, but very rough.  This H=25 object is
> also a VI.
> Cheers, Rob

Hi Rob,

thanks for the news. This guy is well positioned for SALT (B31) so we will
try to observe it photometrically tonight if we manage to get into the queue
on short notice.

Cheers,

Tomek

--
-----------------------------------------------------------------------
   Tomasz Kwiatkowski         Poznan Observatory, A.Mickiewicz University
-----------------------------------------------------------------------

At 03:23 AM 12/1/2008, Robert McNaught wrote:
>   This H=25 object is also a VI.

VI = "very interesting"?  "Six"?  I have trouble understanding my kids'
text messages, too.  What does an Internet-geek mean by "VI"?  sorry, I had
to ask for "LOL" too, a while ago.

Cheers,

Alan

*******************************************************************
Alan W. Harris
Senior Research Scientist
Space Science Institute
4603 Orange Knoll Ave.          Phone:  818-790-8291
La Canada, CA 91011-3364        email:  awharris@...
*******************************************************************

> At 03:23 AM 12/1/2008, Robert McNaught wrote:
>>   This H=25 object is also a VI.

Sorry, VI = Virtual Impactor

At 08:25 AM 12/1/2008, Robert McNaught wrote:
> > At 03:23 AM 12/1/2008, Robert McNaught wrote:
> >>   This H=25 object is also a VI.
>
>Sorry, VI = Virtual Impactor


At 08:32 AM 12/1/2008, John Mahony wrote:
>A few lines selected from the MPES report for this object suggest it means
>"virtual impactor":
>
>------------------------------------------------------
>2008 WY94
>...
>Object is flagged as a Virtual Impactor by SENTRY (JPL) and by CLOMON2
>(NEODyS).

At 09:17 AM 12/1/2008, Fabrizio Bernardi wrote:
>It's a virtual impactor, as you can see on NEODyS
>http://newton.dm.unipi.it/cgi-bin/neodys/neoibo?riskpage:0;main

OK, there seems to be general agreement that "virtual impactor" was
intended by Rob and the MPC, but searching both the MPC site and NEODyS, I
find no exact definition of the intended meaning of "virtual impactor".  I
gather, but am not certain, that the current intent of the term "VI" is the
same as "PHA" but without the restriction of H < 22, that is, a NEA with
MOID < 0.05 but no restriction on size.  Or maybe not, I can't find any
specific definition anywhere.  I hasten to point out that was not the
original intention of the term, as discussed in detail in the following
paper where the term was first used:

Virtual Impactors: Search and Destroy
Andrea Milani, Steven R. Chesley, Andrea Boattini, and Giovanni B. Valsecchi
Icarus, 145, 12-24, 2000.

Briefly, what Milani et al. described was doing a Monte Carlo integration
of many "virtual" objects filling the orbital uncertainty space of an NEA
to identify the "virtual impactors" in the cloud, the ones whose orbits
actually hit the Earth.  One can then run an ephemeris of these "virtual
impactors" and with that in hand go out and search specific spots in the
sky (by radar, or optical) to see if the real asteroid is there.  If so,
the "virtual" asteroid becomes a real, recovered one -- also an impactor;
if not, then we know that the lost asteroid, wherever it is, will not hit
the Earth.  This technique has been used a couple times to certify that
specific lost PHAs are not on a collision course, without actually
recovering them.  So, when the term was originally coined, it had a much
more specific meaning than just any asteroid with a MOID <
0.05.  Apparently the term has been adopted for other service.  I'll only
add that I think it is a poor adoption -- there is nothing virtual about a
real rock sitting out there for all to see.

Cheers,

Alan

*******************************************************************
Alan W. Harris
Senior Research Scientist
Space Science Institute
4603 Orange Knoll Ave.          Phone:  818-790-8291
La Canada, CA 91011-3364        email:  awharris@...
*******************************************************************

At 08:25 AM 12/1/2008, Robert McNaught wrote:
> > At 03:23 AM 12/1/2008, Robert McNaught wrote:
> >>   This H=25 object is also a VI.
>
>Sorry, VI = Virtual Impactor

*******************************************************************
Alan W. Harris
Senior Research Scientist
Space Science Institute
4603 Orange Knoll Ave.          Phone:  818-790-8291
La Canada, CA 91011-3364        email:  awharris@...
*******************************************************************

> OK, there seems to be general agreement that "virtual impactor" was
> intended by Rob and the MPC, but searching both the MPC site and NEODyS, I
> find no exact definition of the intended meaning of "virtual impactor".  I
> gather, but am not certain, that the current intent of the term "VI" is the
> same as "PHA" but without the restriction of H < 22, that is, a NEA with
> MOID < 0.05 but no restriction on size.

It's simpler than that.  If an impact solution exists, such that it gets
listed on the NeoDys and/or Sentry risk pages, then it's considered a VI.
Not quite the same as a PHA, as there are lots of PHAs for which there are
currently no impact solutions, thus they are not VIs.

At 01:03 PM 12/1/2008, Dave Tholen wrote:

>It's simpler than that.  If an impact solution exists, such that it gets
>listed on the NeoDys and/or Sentry risk pages, then it's considered a VI.
>Not quite the same as a PHA, as there are lots of PHAs for which there are
>currently no impact solutions, thus they are not VIs.

Thanks.  It would be nice if the MPC, JPL and DEODyS would put a definition
somewhere in their FAQs page on the web.  But before they set it in stone,
might I suggest "PI", for "potential impactor", instead of "VI".  PI is
more accurately descriptive of what the term is intended to mean.


*******************************************************************
Alan W. Harris
Senior Research Scientist
Space Science Institute
4603 Orange Knoll Ave.          Phone:  818-790-8291
La Canada, CA 91011-3364        email:  awharris@...
*******************************************************************

Hello  Dave,

We and colleagues are preparing to observe this occultation here in Brazil, but
we are in the worst season of the year for Astronomy.

Regards,
Cristovao Jacques
I77




________________________________
De: Dave Herald <drherald@...>
Para: MPML <mpml@yahoogroups.com>
Enviadas: Domingo, 30 de Novembro de 2008 13:12:35
Assunto: {MPML} 20000 VARUNA : Important observation, Dec 7 at 2 hrs UT.


I'm involved with a group that is making a serious effort to observe
occultations TNO
asteroids. A successful observation will directly determine the diameter of the
asteroid.
Additionally, the light curve has the potential to indicate the presence of any
atmosphere
(as in the case of Pluto).

The challenges in observing such an event are huge. Because of their slow motion
and large
distance, there are very few occultations by any one TNO. Also, with a parallax
of only
0.2" or so, a positional uncertainty of 0.2" equates to an uncertainty in the
location of
the occultation path of around the radius of the Earth. And the typical
ephemeris accuracy
of a TNO is somewhat greater than 0.2"!

On December 7 we are confidently predicting an occultation of a mag 14.7 star by
the TNO
20000 Varuna. The occultation path is expected to pass across South America and
southern
Africa. Brazil and Namibia would appear to be the most likely locations.

The text below sets out the activities that have taken place in the last few
weeks to try
to get an accurate prediction for this event. It also include links that give
the latest
predictions of this event. Note that the occultation is predicted to last about
43 secs,
based on an assumed diameter of 900km.

We encourage anyone located in South America or southern Africa to monitor this
event -
noting that the actual path location is still uncertain by perhaps 2000km.

Anyone in those regions that are interested in monitoring this event should
contact
myself, J.Lecacheux, or Bruno Sicardy (see his page below) for any guidance they
might
need.

Dave Herald
Canberra, Australia

----- Original Message -----
From: <jlx@...>
To: <planoccult@AULA. COM>
Sent: Monday, December 01, 2008 1:17 AM
Subject: [PLANOCCULT] News about 20000 VARUNA : an update.

> >From J.Lecacheux.
>
> A tremendous activity followed my private message to Bruno Sicardy (not
> sent to [planoccult] as written in French) about the possible occultation
> of a faint V= 14.7 UCAC star in Gemini by the big TNO (20000) Varuna on
> Dec.07 morning.
>
> Preliminary calculation using "Occult 4" first put the nominal track from
> the Arabic peninsula to Morocco and Florida (USA) with a very large "one
> sigma" uncertainty of 1.2 Re (earth radius), later reduced by S.Preston
> to 0.7 Re. Whole Europe then was concerned by an event of almost uniform
> small probability : for instance between 6 and 11 % from Granada (Spain),
> or between 5 and 9 % from Berlin (Germany).
>
> Then around the last New Moon several observers made "last minute" CCD
> exposures of the V= 18.9 body, namely B.Tregon and F.Colas from Pic-du-Midi
> Observatory (60-cm and 105-cm telescopes), F.Manzini from nw.Italy (40-cm),
> B.Christophe from nw. France (60-cm).
>
> Then the Rio-de Janeiro team led by M.Assafin (Brazil), and R.Behrend from
> Geneva (Switzerland) , made independent astrometric reductions of these data,
> finally obtaining good mutual agreement.
>
> The updated nominal path is shifted by 0".2 or 6000 km south -unfortunately
> for all the European observers-, and now is predicted from the south tip
> of South-Africa (near 02:10 UT in early dawn) to south Brazil (near 02:15
> UT at low elevation).
> In the same time the "one sigma" uncertainty was lowered to 0.12 Re (i.e.
> ten times better than before the new astrometry), whilst in consequence
> the probability of positive detection was boosted greatly.
> Now it could reach up to 44 % from Porto Alegre (south Brazil), 40 % from
> Sao Paulo (Brazil), 37 %  from Capetown (South-Africa) , 14 % from Windhoek
> (Namibia), 8 % from  Recife (nordeste, Brazil), 1.5 % from Belem (Brazil)
> at the Amazon mouth..., and will be fully negligible from any place in the
> northern hemisphere.
> Never any occultation by a Kuiper body, Pluto excepted, reached a likehood
> level so high.
>
> More details may be found at the adresses of Bruno Sicardy (Meudon)
> http://calys. obspm.fr/ ~sicardy/ 07dec08_varuna/ index.html
> and IOTA-ES
> http://varuna. iota-es.de/
>
> VARUNA is a reddish "cubewano" of 280 years period, whose size lies in the
> same class as the biggest classical asteroids, Ceres or Pallas. Its
> rotation period is 6h 21mn. See a preliminary lightcurve on "CdR&CdL" at
> http://obswww. unige.ch/ ~behrend/ page5cou. html#020000
> Note that the occultation time will coincide with a minimum of brightness.
>




       Veja quais são os assuntos do momento no Yahoo! +Buscados
http://br.maisbuscados.yahoo.com

[Non-text portions of this message have been removed]

Hello,

we were just about to start observations of 2008 WY94 when the intrumental
problems appeared (exactly at the hour, when the asteroid was in the
observing window, sigh). Still, we can give it a try tomorrow if someone
sends new astrometry to the MPC and the ephemeris gets recomputed.

The asteroid is approaching the Moon, which is growing in size, so I expect
tomorrow may be the last night to make some photometry of it.

Cheers,

Tomek

--
-----------------------------------------------------------------------
   Tomasz Kwiatkowski         Poznan Observatory, A.Mickiewicz University
-----------------------------------------------------------------------

Hello all,
So VI is not an internet geek word like Alan suspected, it is an asteroid
geek word :)
Now, let's see PHA : perfectly harmless asteroid, it means that such an
asteroid, through perturbations and more perturbations could eventually hit
the earth in the next millions of years. Will very likely not. Come on,
there are about 1000 asteroids already classified as PHAs, how many of these
will really hit the earth in the coming million of years ? less than a
handful, if we are unlucky. That's really an awfully long time. How many in
the next century, none. Unless we are very very very unlucky. We have much
more probability of getting hit by a very small, yet undiscovered asteroid
than by any of these already cataloged PHAs. And that probability is already
very small. I do believe that in all optimistic scenario we have a much
higher probability of destroying us alone before an asteroid falls here, and
nobody is making such fuss about it :).
VI : virtually innocent. Once the orbit has a good quality, might become a
PHA, or just another NEO. The definition David gives does not take at all
any information on the quality of the orbit. I think this is a MAJOR flaw.
If you take just one position of an asteroid and a motion vector, I am
pretty sure you can find a solution to get the thing to impact the Earth
when you want it. So one point no good. But then, 3 or 10 points over a few
nights, are they any better ? What about using the U parameter in the orbit,
and get rid all together of these "virtual impactors" while the orbit is not
known correctly. These words are only good in the Hollywood scenarios, or
the ones made just a little bit more to the east of Hollywood (Pasadena ?).
I have tried over and over to convey the idea that it is time to get serious
about all these things, and stop living in a fantasy world where we believe
a dangerous asteroid will hit us anytime soon. It may give you a reason to
live if you are really a geek and have nothing else in your world, but for a
normal, educated person ?
It is a strange subculture, where you create all the vocabulary for non
existing situations or situations which exist only in your tired brain.
Get your feet on the ground.
So contrarily to Alan I would just scratch the word of any web page, and not
talk about impacts or any word related to impacts where and while there are
none determined, mathematically, with a high degree of confidence. Let's
find words for objects for which a temporary, ultra low probability impact
solution exist, so that people can follow them on, knowing that to a very
high degree of confidence such objects do not hit us, let's just remove the
word PHA, we already have NEOs. Or call NEOs the current PHA and put the
current NEOs in the "asteroid" category. Cataloging an Amor, with a q of 1.3
a "near earth" asteroid is already overdoing it. Near, because in the best
cases it can get to 45 millions of kilometers from the Earth... Some people
really ought to read a bit about very low probability, their perception in
the public, etc... there are mathematicians who have worked on this.
Alain


> -----Original Message-----
> From: mpml@yahoogroups.com [mailto:mpml@yahoogroups.com]On Behalf Of
> Dave Tholen
> Sent: lundi 1 decembre 2008 18:03
> To: mpml@yahoogroups.com
> Subject: Re: {MPML} 2008 WY94 large amplitude fast rotator
>
>
> > OK, there seems to be general agreement that "virtual impactor" was
> > intended by Rob and the MPC, but searching both the MPC site
> and NEODyS, I
> > find no exact definition of the intended meaning of "virtual
> impactor".  I
> > gather, but am not certain, that the current intent of the term
> "VI" is the
> > same as "PHA" but without the restriction of H < 22, that is, a NEA with
> > MOID < 0.05 but no restriction on size.
>
> It's simpler than that.  If an impact solution exists, such that it gets
> listed on the NeoDys and/or Sentry risk pages, then it's considered a VI.
> Not quite the same as a PHA, as there are lots of PHAs for which there are
> currently no impact solutions, thus they are not VIs.
>
> ------------------------------------
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Posts to this list or information found within may be freely
> used, with the stipulation that MPML and the originating author
> are cited as the source of the information.Yahoo! Groups Links
>
>
>

On Mon, 1 Dec 2008, Alan W Harris wrote:

> Thanks.  It would be nice if the MPC, JPL and DEODyS would put
> a definition somewhere in their FAQs page on the web.  But before
> they set it in stone, might I suggest "PI", for "potential
> impactor", instead of "VI".  PI is more accurately descriptive
> of what the term is intended to mean.

Indeed, my use of VI was probably a bit sloppy.  The term refers to an
orbit, not an object, so this is an object with VI orbital solutions...
at least it has today.  I reported a few hours of astrometry from last
night, so tomorrow may have no VI solutions.

Cheers, Rob

I see now where I picked up the usage of VI as meaning the object
rather than orbital solutions.  Entering the object name in the MPC's
Minor Planet and Comet Ephemeris Service gives

     Object is flagged as a Virtual Impactor by SENTRY (JPL) and by
     CLOMON2 (NEODyS).

Cheers, Rob

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Robert H. McNaught
Uppsala Telescope/Siding Spring Survey
Australian National University
Siding Spring Observatory
Coonabarabran, NSW 2357
Australia

P:  +61 2 6842 6260
F:  +61 2 6842 6240

SSS Webpage: http://msowww.anu.edu.au/~rmn/
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

http://dawn.jpl.nasa.gov/mission/journal_11_26_08.asp

Dawn Journal
Dr. Marc Rayman
November 26, 2008

Dear Indawnviduals,

The Dawn spacecraft is healthy and on course for its flyby of Mars
early next year. The planet's gravity will help boost the probe on
its way to rendezvous with Vesta. While the spacecraft has its
sights set on the asteroid belt (via Mars), its path is now
bringing it closer to Earth. Meanwhile, from Earth's perspective,
Dawn appears to be approaching a blindingly close encounter with
the Sun. With so much happening in the solar system, all readers,
whether local or not, are invited to turn their attention here.

In the last log, we saw that Dawn was
nearing the end of an extended period of thrusting with is ion
propulsion system that began on December 17, 2007.  When it left
Earth on September 27, 2007, the Delta II rocket deposited the
spacecraft into a carefully chosen orbit around the Sun. By
October 31, 2008, the spacecraft had completed the thrusting it
needed to change that orbit so it would encounter Mars at just the
right time, location, and angle to sling it on its way to Vesta.
During this interplanetary cruise phase, Dawn thrust for 270 days,
or 85% of the time. Expending less than 72 kilograms (158 pounds)
of xenon propellant, the spacecraft changed its speed by about 1.81
kilometers per second (4050 miles per hour).

Although controlling an interplanetary probe across hundreds of
millions of kilometers (or miles) of deep space and guiding it
accurately enough to reach its remote destination seems as if it
should be a very simple task, readers may be surprised to know
that it is not. Let's consider just one aspect of the problem.

Suppose you want to shoot an arrow at a target. Unlike typical
archers, you are so far from the target that you can only barely
see it. In that case, aiming for the bull's-eye is essentially out
of the question. Adding to the problem may be a variable breeze
that could nudge the arrow off course. Shooting sufficiently
accurately to get the arrow even to the vicinity of the target
would be challenging enough; hitting the precise point you want on
the target is just too difficult.

For readers who are principally interested in archery, this
concludes our in-depth analysis of the sport.

Now let's consider how to change the situation to make it more
similar to an interplanetary mission. If the arrow had a tiny
radio locator mounted on it, you would be able monitor its
progress as it flew closer to the target. This would be like
watching it on a radar screen. You might see your arrow miss the
target entirely or, if you had made a particularly good shot, hit
somewhere on it. Now if you could occasionally send a signal to
the arrow, perhaps to change the angles of the feathers, you might
not be able to alter its course drastically, but you could change
it a little. So if your initial shot had been good enough, you
could guide the arrow to the desired destination. (To buy your
radio controlled archery set, visit the Dawn gift shop on your
planet. The set may be found between the display case with xenon
ion beam jewelry and the shelves and shelves and shelves and
shelves of really cool new Dawn Journal reader action figures --
be sure to buy the one that looks just like you!)

Shooting the arrow is akin to launching a spacecraft, and its
flight to the target represents the interplanetary journey,
although operating a spacecraft involves far greater precision
(and fun!). Our knowledge of where the spacecraft is and where it
is heading is amazingly, fantastically, incredibly accurate, but
it is not perfect. This point is essential. Keeping most
spacecraft on course is a matter of frequently recalculating the
position, speed, and direction of travel and then occasionally
fine-tuning the trajectory through burns of the propulsion system.

Dawn's near-constant use of its advanced ion propulsion system for
most of 2008 changes the story, but only a little. The thrust plan
was calculated before launch and then updated once our arrow was
free of the bow. Throughout the interplanetary cruise phase, a new
thrust plan was transmitted to the spacecraft about every 5 weeks,
each time with slight updates to account for the latest
calculations of Dawn's orbit around the Sun. With this method, the
small adjustments to the trajectory have been incorporated into
the large, preplanned changes.

The mission control team requires about 5 weeks to design,
develop, check, double-check, transmit, and activate a 5-week set
of commands. By the time the spacecraft is executing the final
part of those instructions, it is following a flight plan that is
based on information from 10 weeks earlier. During most of the
mission, when there are months or even years of thrusting ahead of
it, subsequent opportunities to adjust the trajectory are
plentiful. In contrast, for the last period of preplanned
thrusting before Mars, controllers modified their normal process
for formulating the commands, making a fast update for the final
few days of thrusting. By including
the latest navigational data in the computations for the direction
and duration of the concluding segment of powered flight, the
mission control team put Dawn on a more accurate course for Mars
than it otherwise would have been.

Even with this strategy, navigators recognized long ago that
subsequent adjustments would be required. The plan for approaching
Mars has always included windows for trajectory correction
maneuvers (which engineers are physiologically incapable of
calling anything other than TCMs). Dawn's first TCM occurred on
November 20.

As navigators refined their trajectory calculations after
thrusting finished on October 31, they determined that the
spacecraft was quite close to the aim point they wanted, but still
not exactly on target. In fact, rather than being on a course to
sail a few hundred kilometers above Mars, the probe's path would
have taken it to the surface of the planet. Despite the power of
the ion propulsion system, Dawn does not have the capability to
bore through the rocky planet and continue on its way to Vesta.

Such a situation is not surprising. Suppose in the archery, the
bull's-eye were 30 centimeters (1 foot) in diameter, but we
preferred to hit a point 2.2 centimeters (7/8 inch) outside the
bull's-eye, near the 11:00 position (corresponding to where we
want Dawn to fly past Mars). As our arrow approached the target,
it might turn out that it was going to miss the target entirely,
it might be headed for some other point on the target, and it just
might be that it was headed for the bull's-eye itself. Dawn's case
was this last one, so TCM1 put it on track for the destination we
desired.

Amazing sports analogies for the fantastic accuracy of
interplanetary navigation usually fail to account for TCMs, as
most arrows, balls, and other projectiles do not include active
control after they are on their way. Your correspondent has
presented his own simile
<http://nmp.jpl.nasa.gov/ds1/arch/mrlogQ.html> for the astonishing
accuracy with which a spacecraft can reach a faraway destination,
but most such analogies neglect TCMs, without which deep-space
missions could not be accomplished. (Note that the accuracy is
impressive with or without TCMs. We shall extend our archery
example in a future log, making it more quantitative. It will be
important, however, to keep in mind that the ion propulsion system
provides so much maneuvering flexibility that Dawn does not need
to achieve the degree of accuracy in its gravity assist that a
mission using conventional chemical propulsion might.)

For reasons we will not divulge, Dawn's first TCM has been
designated TCM1. On November 20, just as it had for all of its
previous thrusting, the spacecraft pointed a thruster (TCM1 used
thruster #1) in the required direction and resumed emitting the
familiar blue-green beam of xenon ions to alter course. While
typical thrusting during the mission has lasted for almost 7 days
at a time (followed by a hiatus of 7 to 8 hours), in this case
only a short burn was necessary. Propelling itself from about 4:31
pm to 6:42 pm PST was just enough to fine-tune its course and
change its speed by a bit more than 60 centimeters per second (1.3
miles per hour). This adjustment was modest indeed, as at that
time Dawn was traveling around the Sun at more than 22.5
kilometers per second (50,400 miles per hour). Dawn and Mars,
following their separate orbits that will (almost!) intersect on
February 17, 2009, were moving relative to each other at 3.17
kilometers per second (7100 miles per hour).

Dawn's second TCM window (inexplicably named TCM2) is in January.
Traveling two-thirds of the way from here to Mars, the
navigational accuracy then will be still better, with smaller
deviations from the planned target point being detectable, so
another refinement in the trajectory then is likely. In the
meantime, Dawn will follow its orbital path with its ion thrusters
idle.

As Dawn travels through space on its own, its path has been
essentially independent of Earth's. We saw in a previous log
that the weaker grasp exerted by the
Sun at Dawn's greater distance means that it travels more slowly
around the solar system. While Earth has completed more than 1
full revolution (each revolution requiring 1 year) since launch,
Dawn has not yet rounded the Sun once. After receding from the Sun
until early August, the spacecraft began falling back, albeit only
temporarily.

The probe attained its maximum distance from Earth on November 10.
(For anyone who was on Earth on that date and plans to use this
information in an alibi, it may be helpful to know that the
greatest range was reached at about 3:07 am PST.) The spacecraft
was more than 384 million kilometers (239 million miles) from its
one-time home. Although it will make substantial progress on its
journey in the meantime, Dawn's distance to Earth will continue to
decrease until January 2010, when it will be less than one-third
of what it is today. In the summer of that year, however, as Earth
maintains its repetitive annual orbital motion and the explorer
climbs away from the Sun, it will surpass this month's distance to
Earth. (Readers are encouraged to memorize the contents of this
log for reference in 2010 in case we fail to include a link to
this paragraph.)

The complex choreography of the solar system's grand orbital dance
rarely calls for a circular orbit; rather, the dancers follow
ellipses (ovals in which the ends are of equal size) around the
Sun. Thanks to the details of the shapes of their orbits, the
greatest separation between Earth and Dawn did not occur when they
were precisely on opposite sides of the Sun, although the
alignment was close to that.

On December 12, their dance steps will take them to points almost
exactly on opposite sides of the Sun. For observers on Earth, this
is known as solar conjunction, because the spacecraft and the Sun
will appear to be in the same location. (Similarly, from Dawn's
point of view, Earth and the Sun will be almost coincident.) In
reality, of course, Dawn will be much farther away than Earth's
star. It will be 147 million kilometers (91.5 million miles) from
Earth to the Sun but 379 million kilometers (236 million miles)
from the planet to its cosmic envoy.

Its apparent proximity to the Sun presents a helpful opportunity
for terrestrial readers to locate Dawn in the sky. On December 9 -
15, the spacecraft will be less than 1 degree from the Sun,
progressing from east to west and passing just 1/3 degree south of
that brilliant celestial landmark on December 12. (As Dawn does
not orbit in the same plane as Earth, it will not pass directly
behind the Sun.) The Sun itself is 1/2 degree across, so this is
close indeed; the spacecraft will sneak in to less than 1 solar
diameter from the disk. To demonstrate how small the separation
is, if you blocked the Sun with your thumb at arm's length during
this week around conjunction (and you are exhorted to do so), you
also would cover Dawn.

For those interested observers who lack the requisite superhuman
visual acuity to discern the remote spacecraft amidst the dazzling
light of the Sun, conjunction still may provide a convenient
occasion to reflect upon this most recent of humankind's missions
far into the solar system. This small probe is the product of
creatures fortunate enough to be able to combine their powerful
curiosity about the workings of the cosmos with their impressive
abilities to explore, investigate, and ultimately understand.
While its builders remain in the vicinity of the planet upon which
they evolved, their robotic ambassador now is passing on the far
side of the extraordinarily distant Sun. This is the same Sun that
has been the unchallenged master of our solar system for 4.5
billion years. This is the same Sun that has shone down on Earth
throughout that time and has been the ultimate source of so much
of the heat, light, and other energy upon which the planet's
inhabitants have been so dependent. This is the same Sun that has
so influenced human expression in art, literature, and religion
for uncounted millennia. This is the same Sun that has motivated
scientific studies for centuries. This is the same Sun that acts
as our signpost in the Milky Way galaxy. And humans have a
spacecraft on the far side of it. We may be humbled by our own
insignificance in the universe, yet we still undertake the most
valiant adventures in our attempts to comprehend its majesty.

Solar conjunction means even more to Dawn mission controllers than
the opportunity to meditate upon what magnificent feats our
species can achieve. As Earth, the Sun, and the spacecraft come
closer into alignment, radio signals that go back and forth must
pass near the Sun. The solar environment is fierce indeed, and it
causes interference in those radio waves. While some signals will
get through, communications will be less reliable. Therefore,
controllers plan to send no messages to the spacecraft from
December 5 through December 18; all instructions needed during
that time will be stored onboard beforehand. Deep Space Network
antennas, pointing near the Sun, will listen through the roaring
noise for the faint whisper of the spacecraft, but the team will
consider any signals to be a bonus.

There is plenty of other work to do while waiting to resume
communications after conjunction. In addition to preparing for the
visit to Mars, engineers will continue to interpret the results of
election day. On November 4, the Dawn team voted unanimously for
more power. They commanded the spacecraft to execute a set of
steps to yield data that will reveal the full potential of the
enormous solar arrays to generate electrical power. The method was
tested first on July 21, and then refined for a test on September 22.
For this month's measurement, the commands were identical to those
used for the second test with one exception that had been planned
from the beginning: the solar arrays were rotated to point 60
degrees away from the Sun instead of 45 degrees. The solar arrays
are so powerful that when they are pointed directly at the Sun,
the spacecraft could not draw enough power to measure their full
capability.

The data collected show the electrical behavior of the arrays as
the ion propulsion system was commanded through its start-up,
drawing more and more power. Unlike the two tests, this
calibration was designed so that with the arrays pointed so far
from the Sun, they would not be able to provide as much power as
was requested. Engineers wanted to find the point at which the
arrays would no longer be able to satisfy the demands. They were
not disappointed; power climbed up and up until no more was
available. The prospect of having a spacecraft not be able to meet
its own power demands may seem risky, but the procedure was
carefully designed, analyzed, and simulated, and it executed
perfectly. When the ion propulsion system asked for more power
than the arrays could deliver, in the language of the trade, the
solar arrays "collapsed." Now to some (including even some
engineers unfamiliar with the terminology), this suggests
something not entirely desirable, such as 2 bent and twisted
wings, each with 5 warped panels, and 11,480 shattered solar
cells, the fragments sparkling in the sunlight as they tumbled and
floated away from the powerless probe. In this case though,
"collapse" is an electrical, not a mechanical, phenomenon and
hence would be somewhat less visually spectacular and quite
reversible -- a key attribute for a mission with well over 6 years
of space exploration ahead of it. Once all the data are analyzed,
controllers will have a better prediction for how much power the
arrays will be able to generate for the rest of the voyage.

Dawn is 20 million kilometers (12 million miles) from Mars. It is
383 million kilometers (238 million miles) from Earth, or 950
times as far as the moon and 2.59 times as far as the Sun. Radio
signals, traveling at the universal limit of the speed of light,
take 43 minutes to make the round trip.

*preliminary* curve at

http:/www.nmt.edu/~bryan/research/work/mro_images/k08w94y/k08w94y.jpg

period ~ 21-22 min

likely through thin cirrus with more clouds predicted tomorrow.
Therefore, Tomek (or anyone else), this could definitely use more
observations. However, this period info might be useful for your
queue scheduling.

  - Bill Ryan

On Tue, 2 Dec 2008, whrevr wrote:

> *preliminary* curve at
>
> http:/www.nmt.edu/~bryan/research/work/mro_images/k08w94y/k08w94y.jpg
>
> period ~ 21-22 min
>
> likely through thin cirrus with more clouds predicted tomorrow.
> Therefore, Tomek (or anyone else), this could definitely use more
> observations. However, this period info might be useful for your
> queue scheduling.

Hi Bill,

thanks for sharing. It's good you managed to get it. The lightcurve
amplitude is impressive, reminds me of 1620 Geographos. It would be good to
confirm the points at the minima which define the amplitude but are subject
to larger uncertainties.

I have the object scheduled for tonight, the weather forecast is not
optimistic, though.

Cheers,

Tomek

--
-----------------------------------------------------------------------
   Tomasz Kwiatkowski         Poznan Observatory, A.Mickiewicz University
   tkastr@...            http://www.astro.amu.edu.pl/Staff/Tkastr/
-----------------------------------------------------------------------
A clever person solves a problem. A wise person avoids it.  A. Einstein
-----------------------------------------------------------------------

From "Online Etymology Dictionary"
virtual <http://www.etymonline.com/index.php?term=virtual> Look up
virtual at Dictionary.com <http://dictionary.reference.com/search?q=virtual>
     1398, "influencing by physical virtues or capabilities," from M.L.
     virtualis, from L. virtus "excellence, potency, efficacy," lit.
     "manliness, manhood" (see virtue
     <http://www.etymonline.com/index.php?term=virtue>). The meaning of
     "being something in essence or fact, though not in name" is first
     recorded 1654, probably via sense of "capable of producing a certain
     effect" (1432). Computer sense of "not physically existing but made
     to appear by software" is attested from 1959. ...

It looks to me a pertinent wording, but in fact "potential" looks like
having a similar meaning.
The acronym PI, instead, could be confused with PI as Principal
Investigator.
For my personal opinion virtual seems less scary than potential! :-)

Fabrizio Bernardi


Alan W Harris wrote:
>
> At 01:03 PM 12/1/2008, Dave Tholen wrote:
>
> >It's simpler than that. If an impact solution exists, such that it gets
> >listed on the NeoDys and/or Sentry risk pages, then it's considered a VI.
> >Not quite the same as a PHA, as there are lots of PHAs for which
> there are
> >currently no impact solutions, thus they are not VIs.
>
> Thanks. It would be nice if the MPC, JPL and DEODyS would put a
> definition
> somewhere in their FAQs page on the web. But before they set it in stone,
> might I suggest "PI", for "potential impactor", instead of "VI". PI is
> more accurately descriptive of what the term is intended to mean.
>
> *******************************************************************
> Alan W. Harris
> Senior Research Scientist
> Space Science Institute
> 4603 Orange Knoll Ave. Phone: 818-790-8291
> La Canada, CA 91011-3364 email: awharris@...
> <mailto:awharris%40SpaceScience.org>
> *******************************************************************
>
>

Hi Tomek --

Bummer . .  I'm not optimistic either about our weather tomorrow
night. Hopefully it will clear at SALT for you. I jumped on this
tonight after reading your message that you couldn't observe it.
However, as indicated in my previous message, it wasn;t really a good
photometry night since I know that there were cirrus around. I'm
still observing so I haven't gotten a chance to
look carefully at my comp stars to see how bad the sky really was.

Yes - the amplitude is impressive, but it is also at a pretty large
phase angle.

Good luck tomorrow night!!

  - Bill

--- In mpml@yahoogroups.com, Tomasz Kwiatkowski <tkastr@...> wrote:
>
> On Tue, 2 Dec 2008, whrevr wrote:
>
> > *preliminary* curve at
> >
> > http:/www.nmt.edu/~bryan/research/work/mro_images/k08w94y/k08w94y.jpg
> >
> > period ~ 21-22 min
> >
> > likely through thin cirrus with more clouds predicted tomorrow.
> > Therefore, Tomek (or anyone else), this could definitely use more
> > observations. However, this period info might be useful for your
> > queue scheduling.
>
> Hi Bill,
>
> thanks for sharing. It's good you managed to get it. The lightcurve
> amplitude is impressive, reminds me of 1620 Geographos. It would be
good to
> confirm the points at the minima which define the amplitude but are
subject
> to larger uncertainties.
>
> I have the object scheduled for tonight, the weather forecast is not
> optimistic, though.
>
> Cheers,
>
> Tomek
>
> --
> -----------------------------------------------------------------------
>   Tomasz Kwiatkowski         Poznan Observatory, A.Mickiewicz University
>   tkastr@...            http://www.astro.amu.edu.pl/Staff/Tkastr/
> -----------------------------------------------------------------------
> A clever person solves a problem. A wise person avoids it.  A. Einstein
> -----------------------------------------------------------------------
>

Bill,

Nice curve.

It will be important to confirm the amplitude (and period - of course),
which appears to be about 1.8 mag. This would make it among the largest
amplitudes in the Asteroid Lightcurve Database

   <http://www.minorplanetobserver.com/astlc/LCLIST_PUB_NOV2008.zip>


Here's a listing of those objects with a maximum amplitude > 1.5 mag.


NUMBER NAME                 AMPMAX
---------------------------------
        2006 BQ6             1.6
   3102 Krok                 1.6
        2000 EB14            1.7
163732 2003 KP2             1.7
        1995 HM              2.
        2003 NZ6             2.
        2005 WC1             2.
        2002 TD60            2.0
        2005 UE1             2.0
   1620 Geographos           2.03
   1865 Cerberus             2.10


It will also be nice to see this published sometime (hint! hint! <g>)


Clear Skies,
Brian D. Warner
Palmer Divide Observatory
http://www.MinorPlanetObserver.com

Collaborative Asteroid Lightcurve Link (CALL)
http://www.MinorPlanetObserver.com/astlc/default.htm

For those with larger scopes, a possible fast rotator. Those who can
stack and track, an interesting target. About 2.5 lunar distances.


Ephemeris:
2008 XK                  a,e,i = 2.36, 0.62, 6                   q = 0.8978
Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase     V
2008 11 30    03 28.05   +01 10.6    0.0466   1.029   155.3    23.6    21.7
2008 12 01    03 31.87   +01 23.5    0.0397   1.022   155.3    23.8    21.4
2008 12 02    03 37.36   +01 43.1    0.0328   1.016   155.6    23.7    20.9
2008 12 03    03 45.83   +02 14.2    0.0259   1.010   156.4    23.0    20.4
2008 12 04    04 00.41   +03 08.5    0.0192   1.003   158.4    21.2    19.7
2008 12 05    04 30.79   +04 59.6    0.0126   0.997   162.2    17.6    18.6
2008 12 06    06 01.50   +09 51.1    0.00666  0.992   158.9    20.9    17.3
2008 12 07    10 49.48   +13 09.1    0.00520  0.986    96.4    83.3    18.7
2008 12 08    13 20.34   +06 49.2    0.0103   0.980    61.2   118.2    21.9
2008 12 09    14 03.18   +04 17.9    0.0167   0.975    51.8   127.4    23.7
2008 12 10    14 21.82   +03 08.0    0.0235   0.969    48.3   130.7    24.8

Timothy B. Spahr             (C) Copyright 2008 MPC           M.P.E.C. 2008-X23


Clear Skies,
Brian D. Warner
Palmer Divide Observatory
http://www.MinorPlanetObserver.com

Collaborative Asteroid Lightcurve Link (CALL)
http://www.MinorPlanetObserver.com/astlc/default.htm

Missing piece of information:  H = 27.2

At 09:00 AM 12/2/2008, Brian D. Warner wrote:
>For those with larger scopes, a possible fast rotator. Those who can
>stack and track, an interesting target. About 2.5 lunar distances.
>
>
>Ephemeris:
>2008 XK                  a,e,i = 2.36, 0.62, 6                   q = 0.8978
>Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase     V
>2008 11 30    03 28.05   +01 10.6    0.0466   1.029   155.3    23.6    21.7
>2008 12 01    03 31.87   +01 23.5    0.0397   1.022   155.3    23.8    21.4
>2008 12 02    03 37.36   +01 43.1    0.0328   1.016   155.6    23.7    20.9
>2008 12 03    03 45.83   +02 14.2    0.0259   1.010   156.4    23.0    20.4
>2008 12 04    04 00.41   +03 08.5    0.0192   1.003   158.4    21.2    19.7
>2008 12 05    04 30.79   +04 59.6    0.0126   0.997   162.2    17.6    18.6
>2008 12 06    06 01.50   +09 51.1    0.00666  0.992   158.9    20.9    17.3
>2008 12 07    10 49.48   +13 09.1    0.00520  0.986    96.4    83.3    18.7
>2008 12 08    13 20.34   +06 49.2    0.0103   0.980    61.2   118.2    21.9
>2008 12 09    14 03.18   +04 17.9    0.0167   0.975    51.8   127.4    23.7
>2008 12 10    14 21.82   +03 08.0    0.0235   0.969    48.3   130.7    24.8
>
>Timothy B. Spahr             (C) Copyright 2008 MPC           M.P.E.C.
>2008-X23

*******************************************************************
Alan W. Harris
Senior Research Scientist
Space Science Institute
4603 Orange Knoll Ave.          Phone:  818-790-8291
La Canada, CA 91011-3364        email:  awharris@...
*******************************************************************

http://www.lowell.edu/media/releases.php?release=20081202

FOR IMMEDIATE RELEASE
December 2, 2008

A New Compositional Class of Comets: from Fire, Ice, or Beyond?
Lowell Observatory Astronomer Confirms New Class of Comets

Flagstaff, Ariz. -- Comet 96P/Machholz 1 shows extremely anomalous
compositional characteristics helping pinpoint its origin to one of
three intriguing scenarios. David Schleicher, Lowell Observatory
planetary astronomer, measured abundances of five molecular species in
the comae of 150 comets and discovered that one comet, 96P/Machholz 1,
has an extremely unusual chemistry. The exact cause of this chemical
anomaly remains unknown, but each of three possible explanations will
yield important but differing new constraints on the formation or
evolution of comets. The study is published in the November issue of the
Astronomical Journal.

The discovery of comet Machholz 1's extremely anomalous composition
reveals the existence of a new class of comets. Astronomers identified
two other classes in the 1990s. While Machholz 1 also has strongly
depleted C2 and C3 carbon species, what makes it anomalous is that the
molecule cyanogen, CN, is extremely depleted. In Machholz 1 CN is
missing by about a factor of 72 from the average of other comets, i.e.,
only a little above one percent of normal. "This depletion of CN is much
more than ever seen for any previously studied comet, and only one other
comet has even exhibited a CN depletion," said Schleicher.

One possible explanation is that Machholz 1 did not originate in our
Solar System, but instead escaped from another star. In this scenario,
the other star's proto-planetary disk might have had a lower abundance
of carbon, resulting in all carbon-bearing compounds having lower
abundances. "A large fraction of comets in our own Solar System have
escaped into interstellar space, so we expect that many comets formed
around other stars would also have escaped," said Schleicher. "Some of
these will have crossed paths with the sun, and Machholz 1 could be an
interstellar interloper."

Another possible explanation for Machholz 1's anomalous composition is
that it formed even further from the sun in a colder or more extreme
environment than another other comet we have studied thus far. If this
was the case, then the scarcity of such objects is likely associated
with the significant difficulty of explaining how such comets moved into
the inner solar system where they can then be discovered and observed.

A third possibility is that Machholz 1 originated as a carbon-chain
depleted comet but that its chemistry was subsequently altered by
extreme heat. While no other comet has exhibited changes in chemistry
due to subsequent heating by the sun, Machholz 1 has the distinction of
having an orbit that now takes it to well inside Mercury's orbit every
five years. (Other comets get even closer to the sun, but not as often).
"Since its orbit is unusual, we must be suspicious that repeated high
temperature cooking might be the cause for its unusual composition,"
said Schleicher. "However, the only other comet to show depletion in the
abundance of CN did not reach such high temperatures. This implies that
CN depletion does not require the chemical reactions associated with
extreme heat."

Although comet 96P/Machholz 1 was first sighted in 1986 and orbits the
sun with a period of slightly over five years, compositional
measurements only took place during the comet's recent 2007 apparition.
Lowell Observatory's program of compositional studies, currently headed
by Schleicher, includes measurements of over 150 comets obtained during
the past 33 years. This research is unique because it compares and
contrasts Machholz 1 against this large database of 150 comets.

In the early 1990s, Lowell Observatory's long-term program first
identified the existence of two compositional classes of comets. One
class, containing the majority of observed comets, has a composition
called "typical." Most members of this typical class have long resided
in the Oort Cloud at the very fringes of our Solar System but are
believed to have originally formed amidst the giant planets,
particularly between Saturn, Uranus, and Neptune. Other members of this
compositional class arrived from the Kuiper Belt, located just beyond
Neptune.

The second compositional class of comets has varying depletions in two
of the five chemical species measured. Since both depleted molecules, C2
and C3, are wholly composed of carbon atoms, this class was named
"carbon-chain depleted." Moreover, nearly all comets in this second
class have orbits consistent with their having arrived from the Kuiper
Belt. For this and other reasons, the cause of the depletion is believed
to be associated with the conditions that existed when the comets
formed, perhaps within an outer, colder region of the Kuiper Belt.

Comets are widely thought to be the most pristine objects available for
detailed study remaining from the epoch of Solar System formation. As
such, comets can be used as probes of the proto-planetary material that
was incorporated into our Solar System. Differences in the current
chemical composition among comets can indicate either differences in
primordial conditions or evolutionary effects.

Although the location of origin cannot be definitively determined for
any single comet, Machholz 1's short orbital period means that
astronomers can search for additional carbon-bearing molecular species
during future apparitions. "If additional carbon-bearing species are
also strongly depleted, then the case for its origin outside of our
Solar System would be strengthened," said Schleicher. The next
opportunity for observations will be in 2012.

This research is supported by NASA's Planetary Astronomy and Planetary
Atmospheres Programs.

The study is published in the November issue of the Astronomical
Journal. <http://www.iop.org/EJ/abstract/1538-3881/136/5/2204>

FOR MORE INFORMATION

Scientific contact: David Schleicher (dgs@...) (928) 233-3228

See a pdf of the report, Lowell Observatory Comet 96/P Machholz 1
Background
<http://www.lowell.edu/media/content/release_supplements/Mach1_backgrd.pdf>


About Lowell Observatory

Lowell Observatory is a private, non-profit research institution founded
in 1894 by Percival Lowell. The Observatory has been the site of many
important findings including the discovery of the large recessional
velocities (redshift) of galaxies by Vesto Slipher in 1912-1914 (a
result that led ultimately to the realization the universe is
expanding), and the discovery of Pluto by Clyde Tombaugh in 1930. Today,
Lowell's 20 astronomers use ground-based telescopes around the world,
telescopes in space, and NASA planetary spacecraft to conduct research
in diverse areas of astronomy and planetary science. The Observatory
welcomes more than 75,000 visitors each year to its Mars Hill campus in
Flagstaff, Arizona for a variety of tours, telescope viewing, and
special programs. Lowell Observatory currently has four research
telescopes at its Anderson Mesa dark sky site east of Flagstaff, and is
building a 4-meter class research telescope, the Discovery Channel
Telescope, in partnership with Discovery Communications.

CONTACT

Steele Wotkyns
steele@...
(928) 233-3232

end

I was just reading the NOMAD catalog.  At the risk of showing my
ignorance, I'd never heard of NOMAD before.  Maybe because it's 100 GB.

But with the cost of storage continuing to go down I'm guessing it
wont be that long before I'll have a drive big enough to hold it.

But then I also read that the much smaller UCAC-3 "is expected to be
distributed in early 2009". (http://ad.usno.navy.mil/ucac/)

So my question is, for my photometric and astrometric work, will UCAC
suffice or should I maybe start thinking about NOMAD?

Thanks,

patrick

NOMAD inherits all the "funnies" of the catalogues it is
compiled from, and provides no improvements.  (It is a compilation,
not something newly generated.)  I would avoid it.  UCAC3 will be
great to have, but given that the "any day now" claim has been
made for some years, I wouldn't hold your breath waiting for it.
      Certainly NOMAD is no good for photometry.  For that you might
be able to use the intersection of SDSS DR6 + CMC14, adopting the
Sloan r' magnitudes for general use.

\Brian


On Tue, 2008-12-02 at 17:36 -0700, Patrick Wiggins wrote:
> I was just reading the NOMAD catalog.  At the risk of showing my
> ignorance, I'd never heard of NOMAD before.  Maybe because it's 100 GB.
>
> But with the cost of storage continuing to go down I'm guessing it
> wont be that long before I'll have a drive big enough to hold it.
>
> But then I also read that the much smaller UCAC-3 "is expected to be
> distributed in early 2009". (http://ad.usno.navy.mil/ucac/)
>
> So my question is, for my photometric and astrometric work, will UCAC
> suffice or should I maybe start thinking about NOMAD?
>
> Thanks,
>
> patrick
>
> ------------------------------------
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Posts to this list or information found within may be freely used, with the
stipulation that MPML and the originating author are cited as the source of the
information.Yahoo! Groups Links
>
>
>

Bear in mind also that the UCAC is an astrometric catalog, not a photometric
one.  Norbert Zacharias has never asserted that the photometry is better than
a few tenths of a magnitude, especially in the northern hemisphere.  Many of
their images were taken with poor skies.

Yeah, I'm waiting with bated breath for UCAC3 too....

-- Bill Owen

On Tuesday 02 December 2008 4:50 pm, Brian Skiff wrote:
>      NOMAD inherits all the "funnies" of the catalogues it is
> compiled from, and provides no improvements.  (It is a compilation,
> not something newly generated.)  I would avoid it.  UCAC3 will be
> great to have, but given that the "any day now" claim has been
> made for some years, I wouldn't hold your breath waiting for it.
>      Certainly NOMAD is no good for photometry.  For that you might
> be able to use the intersection of SDSS DR6 + CMC14, adopting the
> Sloan r' magnitudes for general use.
>
> \Brian
>
> On Tue, 2008-12-02 at 17:36 -0700, Patrick Wiggins wrote:
> > I was just reading the NOMAD catalog.  At the risk of showing my
> > ignorance, I'd never heard of NOMAD before.  Maybe because it's 100 GB.
> >
> > But with the cost of storage continuing to go down I'm guessing it
> > wont be that long before I'll have a drive big enough to hold it.
> >
> > But then I also read that the much smaller UCAC-3 "is expected to be
> > distributed in early 2009". (http://ad.usno.navy.mil/ucac/)
> >
> > So my question is, for my photometric and astrometric work, will UCAC
> > suffice or should I maybe start thinking about NOMAD?
> >
> > Thanks,
> >
> > patrick
> >
> > ------------------------------------
> >
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > Posts to this list or information found within may be freely used, with
> > the stipulation that MPML and the originating author are cited as the
> > source of the information.Yahoo! Groups Links

My views:
1. NOMAD is a merged catalogue. It attempts to combine the positions and
magnitudes of
stars from the most reliable sources. It applies a different hierarchy to the
positions
than to magnitudes.
2. For accurate astrometry, UCAC2 is still the best catalogue. CMC-14 has
absolute
positions that are almost as good, but there are no proper motions. PPMX
superficially
looks to be useful, but most positions are very close to UCAC positions. Also
its greatest
precision is limited to stars brighter than 12.5. And for stars that are not in
UCAC2 the
accuracy is not good.
3. The advantage of NOMAD (from my perspective) is that when the field is sparse
of
reference stars (an issue with small-field imaging), you do not need to change
reference
catalogues from UCAC to something else (eg USNO-B1). By using NOMAD, you use
UCAC2
positions whenever they are available - and typically USNO-B1 otherwise. [In
this
situation, I should note that if the region is covered by CMC-14, that catalogue
would be
preferable.] I should note that in my system (10 x 15' field) I occasionally
have
situations where the number of UCAC2 stars that are present in the field is just
1.
4.. For info - a check of the 2008 Nov MPC summary showed that NOMAD was listed
by 20
stations as a catalogue used.  CMC14 was listed against 8.
5. On UCAC3. My understanding of the current status is that (i) the catalogue
positions at
epoch have been finalised (with some improvements in the position determination
over
UCAC2), and that (ii) they are currently working on the proper motions. As in
any IT
project, time lines inevitably stretch. Don't expect the catalogue to issue in
the next
few months. Also, expect it to issue as a single DVD, with a different data
format.

Finally, NOMAD is accessible via Vizier - and Astrometrica accesses the
catalogue from
there when using it for astrometric reductions. It is available from USNO - with
you
providing the drive, and covering the mailing costs - but I'm sure they don't
want to be
swamped with requests. The catalogue is ~95GB, and fits nicely on a USB drive.
But Vizier
access is preferable unless you have a need for high-speed access (which is an
issue if
you are searching for asteroid occultations, for example).



Dave Herald
Canberra, Australia


----- Original Message -----
From: "Patrick Wiggins" <paw@...>
To: "mpml (list) mpml" <mpml@yahoogroups.com>
Sent: Wednesday, December 03, 2008 11:36 AM
Subject: {MPML} NOMAD vs. UCAC


>I was just reading the NOMAD catalog.  At the risk of showing my
> ignorance, I'd never heard of NOMAD before.  Maybe because it's 100 GB.
>
> But with the cost of storage continuing to go down I'm guessing it
> wont be that long before I'll have a drive big enough to hold it.
>
> But then I also read that the much smaller UCAC-3 "is expected to be
> distributed in early 2009". (http://ad.usno.navy.mil/ucac/)
>
> So my question is, for my photometric and astrometric work, will UCAC
> suffice or should I maybe start thinking about NOMAD?
>
> Thanks,
>
> patrick
>
> ------------------------------------
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Posts to this list or information found within may be freely used, with the
stipulation
> that MPML and the originating author are cited as the source of the
information.Yahoo!
> Groups Links
>
>
>

> I was just reading the NOMAD catalog.  At the risk of showing my
> ignorance, I'd never heard of NOMAD before.  Maybe because it's 100 GB.

The vast majority of the NOMAD catalog is just the USNO-B1.0 catalog.
NOMAD adds the brighter stars from other catalogs and attempts to
use the best catalog for those stars that the B1.0 has in common with
other catalogs.

> So my question is, for my photometric and astrometric work, will UCAC
> suffice or should I maybe start thinking about NOMAD?

For photometric work, neither suffices.  For astrometric work, the
choice depends on your field of view, the depth to which you are
working, and the amount of field distortion.  The more distortion
you have, the more reference stars you'll need to solve for the
distortion coefficients.  If your field is too small, the UCAC may
not provide a sufficient number of reference stars to perform the
solution.  And if you work really faint by taking long exposures,
UCAC stars might saturate.

The sky coverage of UCAC2 is shown graphically at:
http://ad.usno.navy.mil/ucac/skycov_u2c.gif

There has been no change since its release.

Dave Herald
Canberra, Australia


----- Original Message -----
From: "Robert Crawford" <rincon-ranch@...>
To: "Dave Herald" <drherald@...>; "mpml (list) mpml"
<mpml@yahoogroups.com>;
"Patrick Wiggins" <paw@...>
Sent: Thursday, December 04, 2008 2:00 AM
Subject: RE: {MPML} NOMAD vs. UCAC


> OK.  We should install UCAC2 on your laptops as backup.  Its only limitation
> is that the catalog does not currently go above about +40 dec.  I'll double
> check that on the web to make sure it is still true.
>
> RWC
>
>  -----Original Message-----
>  From: mpml@yahoogroups.com [mailto:mpml@yahoogroups.com]On Behalf Of Dave
> Herald
>  Sent: Tuesday, December 02, 2008 18:48
>  To: mpml (list) mpml; Patrick Wiggins
>  Subject: Re: {MPML} NOMAD vs. UCAC
>
>
>  My views:
>  1. NOMAD is a merged catalogue. It attempts to combine the positions and
> magnitudes of
>  stars from the most reliable sources. It applies a different hierarchy to
> the positions
>  than to magnitudes.
>  2. For accurate astrometry, UCAC2 is still the best catalogue. CMC-14 has
> absolute
>  positions that are almost as good, but there are no proper motions. PPMX
> superficially
>  looks to be useful, but most positions are very close to UCAC positions.
> Also its greatest
>  precision is limited to stars brighter than 12.5. And for stars that are
> not in UCAC2 the
>  accuracy is not good.
>  3. The advantage of NOMAD (from my perspective) is that when the field is
> sparse of
>  reference stars (an issue with small-field imaging), you do not need to
> change reference
>  catalogues from UCAC to something else (eg USNO-B1). By using NOMAD, you
> use UCAC2
>  positions whenever they are available - and typically USNO-B1 otherwise.
> [In this
>  situation, I should note that if the region is covered by CMC-14, that
> catalogue would be
>  preferable.] I should note that in my system (10 x 15' field) I
> occasionally have
>  situations where the number of UCAC2 stars that are present in the field
> is just 1.
>  4.. For info - a check of the 2008 Nov MPC summary showed that NOMAD was
> listed by 20
>  stations as a catalogue used. CMC14 was listed against 8.
>  5. On UCAC3. My understanding of the current status is that (i) the
> catalogue positions at
>  epoch have been finalised (with some improvements in the position
> determination over
>  UCAC2), and that (ii) they are currently working on the proper motions. As
> in any IT
>  project, time lines inevitably stretch. Don't expect the catalogue to
> issue in the next
>  few months. Also, expect it to issue as a single DVD, with a different
> data format.
>
>  Finally, NOMAD is accessible via Vizier - and Astrometrica accesses the
> catalogue from
>  there when using it for astrometric reductions. It is available from
> USNO - with you
>  providing the drive, and covering the mailing costs - but I'm sure they
> don't want to be
>  swamped with requests. The catalogue is ~95GB, and fits nicely on a USB
> drive. But Vizier
>  access is preferable unless you have a need for high-speed access (which
> is an issue if
>  you are searching for asteroid occultations, for example).
>
>  Dave Herald
>  Canberra, Australia
>
>  ----- Original Message -----
>  From: "Patrick Wiggins" <paw@...>
>  To: "mpml (list) mpml" <mpml@yahoogroups.com>
>  Sent: Wednesday, December 03, 2008 11:36 AM
>  Subject: {MPML} NOMAD vs. UCAC
>
>  >I was just reading the NOMAD catalog. At the risk of showing my
>  > ignorance, I'd never heard of NOMAD before. Maybe because it's 100 GB.
>  >
>  > But with the cost of storage continuing to go down I'm guessing it
>  > wont be that long before I'll have a drive big enough to hold it.
>  >
>  > But then I also read that the much smaller UCAC-3 "is expected to be
>  > distributed in early 2009". (http://ad.usno.navy.mil/ucac/)
>  >
>  > So my question is, for my photometric and astrometric work, will UCAC
>  > suffice or should I maybe start thinking about NOMAD?
>  >
>  > Thanks,
>  >
>  > patrick
>  >
>  > ------------------------------------
>  >
>  > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>  >
>  > Posts to this list or information found within may be freely used, with
> the stipulation
>  > that MPML and the originating author are cited as the source of the
> information.Yahoo!
>  > Groups Links
>  >
>  >
>  >
>
>
>
>
>

A meteor is being credited with turning on an eerie show south of Auckland.

Just after sunset a bright line could be seen in the sky for several minutes
above the horizon.

A spokesman for the Stardome Observatory in Auckland says he believes it was
a meteor entering the earth's atmosphere. He estimates it was about the size
of a grapefruit, and the visible line was a result of the explosion created
as the meteor disintegrated at an altitude of about 120 kilometres.

http://www.newstalkzb.co.nz/newsdetail1.asp?storyID=148970







[Non-text portions of this message have been removed]

Here is another object that may be of interest to photometrists
with "bigger toys."

{Portions forwarded under "fair use" concept. Please note the
  copyright and give proper attribution}


Clear Skies,
Brian D. Warner
Palmer Divide Observatory
http://www.MinorPlanetObserver.com

Collaborative Asteroid Lightcurve Link (CALL)
http://www.MinorPlanetObserver.com/astlc/default.htm


Orbital elements:
2008 XC1                                                 Earth MOID = 0.0062 AU
Epoch 2008 Nov. 30.0 TT = JDT 2454800.5                 MPC
M 343.82368              (2000.0)            P               Q
n   0.34277714     Peri.   42.23414     -0.63329970     -0.77032456
a   2.0220636      Node    87.19797     +0.68864959     -0.60477406
e   0.5700707      Incl.    4.27040     +0.35311930     -0.20210990
P   2.88           H   23.1           G   0.15           U   9

Ephemeris:
2008 XC1                 a,e,i = 2.02, 0.57, 4                   q = 0.8693
Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase     V
2008 11 30    04 16.14   +04 18.8    0.0936   1.076   162.5    16.0    19.0
2008 12 01    04 18.03   +03 59.2    0.0864   1.069   162.0    16.6    18.8
2008 12 02    04 20.27   +03 37.0    0.0792   1.061   161.4    17.3    18.6
2008 12 03    04 22.96   +03 11.2    0.0720   1.054   160.7    18.0    18.4
2008 12 04    04 26.26   +02 40.7    0.0649   1.047   160.1    18.7    18.2
2008 12 05    04 30.38   +02 03.7    0.0579   1.040   159.3    19.6    18.0
2008 12 06    04 35.66   +01 17.5    0.0509   1.033   158.5    20.5    17.7
2008 12 07    04 42.61   +00 17.9    0.0440   1.026   157.5    21.6    17.4
2008 12 08    04 52.15   -01 02.5    0.0372   1.019   156.2    23.0    17.1
2008 12 09    05 05.94   -02 57.0    0.0305   1.012   154.2    25.0    16.7
2008 12 10    05 27.39   -05 51.3    0.0241   1.006   150.9    28.5    16.3
2008 12 11    06 04.24   -10 36.7    0.0181   0.999   144.1    35.3    15.8
2008 12 12    07 15.40   -18 31.8    0.0132   0.993   129.4    50.0    15.6
2008 12 13    09 30.20   -27 22.9    0.0110   0.987   101.6    77.8    16.0
2008 12 14    11 59.41   -27 19.2    0.0129   0.981    72.6   106.7    17.6
2008 12 15    13 24.92   -22 37.8    0.0177   0.974    56.1   123.0    19.4
2008 12 16    14 08.32   -18 57.1    0.0236   0.969    48.2   130.8    20.7
2008 12 17    14 32.93   -16 30.5    0.0300   0.963    44.2   134.6    21.6
2008 12 18    14 48.51   -14 51.0    0.0366   0.957    42.1   136.4    22.2
2008 12 19    14 59.22   -13 40.6    0.0434   0.952    41.1   137.2    22.7
2008 12 20    15 07.05   -12 48.7    0.0503   0.946    40.6   137.4    23.0

Timothy B. Spahr             (C) Copyright 2008 MPC           M.P.E.C. 2008-X34