System Occults UCAC
June 12th 2006, 16h
At the moment, not all graphs, maps and informations are
But they will be presented soon.
The Pluto system will occult the star
UCAC 2603 9859 (15mag)
12th, 2006 around 16h 25min UTC,
as first pointed out by Dave Herald (WINOCCULT, DE405) and
Jean Lecacheux in early March. A new prediction
for this important
occultation has been done by Bruno
Sicardy, Observatoire d Paris/Meudon using DE413 and an improved
ephemeris of P1 and P2. The main
visibility areas of the occultation by Pluto itself will be New
Zealand, Tasmania, southern Australia and Reunion.
Even more important, following the discovery of the recently discovered
small satellites P2, an occultation of this small body will take place
about 1000km north of Pluto's occultation track.
The scientific goals of an observation of this important occultation
determine the atmospheric static conditions (Temperature, Pressure
etc.) and to
compare it with data from past occultations, to get an idea of the
development of Pluto's atmosphere during the loss of energy due to the
increasing distance from the sun.
- to determine winds in Pluto's atmosphere by a possible
of a central flash from Tasmania or
- For P2 and other
possible objects as well
- to determine the diameter of P2
- to determine the mean density of P2
- to determine a possible ring system around Pluto
The results are of special interest
to the New Horizons mission to Pluto, because possible smaller bodies
and/or a ring system around Pluto may have a significant impact on the
In order to observe the small
satellite P2 by this occultation, a lot of stations is necessary. The
approximate diameter of P2 is only around 100 km. So it will be a real
challange. Everybody in the area of Central and Southern Australia,
Tasmania but also on Reunion is encouraged to observe! IOTA-ES
will try to coordinate together with other organizations as well the
preparations and obervations for the event. Obervations by the team
around Bruno Sicardy are planned in Tasmania and New Zealand.
The event carries the number P384.2
on the MIT
The occultation track
Bruno Sicardy calculated the following map for the occultation
B. Sicardy reports, that the above prediction is an update to older
ones in the sense that they include the O-C offset
observed last year on Charon (ra:+0.022 de:-0.012). Otherwise
there is no update for the star position, the position ist still based
on observations by R. Behrend, ESO 1.2m telescope) .
Because of the earth's rotation, for Reunion's occultation by
P2 there is a slightly other view for an occultation time of
16:07, which is presented in the prediction below:
This prediction by B. Sicardy, Observatoire d' Paris-Meudon, is
on observations from La Silla's suisse 1.2m
telescope on April 2nd 2006 and has been reported by Raoul Behrend. The
red stars mark the positions of larger observatories in the area.
This image will be updated, as soon as new predictions are coming in.
Different groups have plans to observe
this occultation, including Bruno
Sicardy for the observatory Paris/Meudon. IOTA-ES will try to
coordinate observations by amateurs and Professional astronomers in the
described area, and may organize an own
expedition. Contacts to observatories and interested amateurs in the
area will be established.
In case of an own expedition, we are looking for cooperation
partners in Australia and New Zealand, who can
support such an expedition with logistics, transportation and
Because of the faintness of the star and the Pluto
system, it is to be expected, that the minimum telescope size for
observation will be around 25cm. Because of the very unfavorable
position of the occulted star in the sky right now, there are no
precise photometric measurements with IOC cameras right now. As soon as
photometry is available, it will be presented here.
The track will
be updated as soon
as new predictions become available.
Details of the Pluto
following graph shows the Pluto system, as it looks at the time of
Calculated by Bruno Sicardy, Observatoire d Paris-Meudon. The red
line is the projection of the star as seen from an observer in Hobart,
From Raymond Dusser a nice drawing, adopted from M. Buie has been sent
in together with a good explanation for the situation of the system
with the 4 bodies:
the occultation looks from either Hobart or New Zealand (Mt. John), can
be seen below. You also see the "miss" of Pluto itself from Reunion.
Here is the latest prediction
for the P2 occultation, issued from B. Sicardy on the 28th of May. The
asteriks show possible observing sites.
Go to TOP
Images with different cameras
Using a MINTRON 1/2 inch EXVIEW Chip camera with 48x integration
time (equivalent to about 1 second) images of Pluto and the target star
have been recorded with an 11 inch Schmidt Cassegrain telescope from
Munich on the 3rd of May, 2006. No extra filter has been used. Pluto
was only about 22 degrees high, therefore the airmass is pretty high.
The focal length was about 900mm at 1/3 focal ratio. Because the site
of the telescope was only 5 km south-east of the city center of Munich,
background light was very high. Therefore no precise magnitudes can be
given. It is expected, that the same quality of image can be reached in
Tasmania/New Zealand with about 1/4th of the integration time.
Here is an image from the target
star with the same conditions as above.
Here we have new images with the IOTA Occultation Camera (IOC),
each with 4 seconds exposure time and 1800mm focal length.
And here the target star, very faint, because of the high
background due to the city lights from Munich (Only 5km away from the
center of Munich and only 22 deg high.
From Jean Lecacheux, a 3' time 3' image of the target area
including the target star is shown in the following image:
Dave Gault from Australia got
an interesting image recently from the target star with an 10 inch SCT
telescope. He used the black and white version of the DSI camera from
Meade with an exposure time of 1 second. You can see this fine image here
. The image has been taken only 20 degrees away from the near full moon
(about 20 degrees distance)! Therefore the situation is very similar to
the real event on the 12th of June!
Pluto and the target star
Photometry of Pluto and the target star with small telescopes from
central Europe is very complicated, because Pluto has an maximal
altitude of about 25 deg this year. The problems arise even more, if
the telescope is in or near a big city (such as Munich!). A lot of
extra haze and the city lights generate a big problem for precise
However, at high altitudes and far away from big cities at Pic du
Midi, Jean Lecacheaux got the following BVRI photometry of Pluto and
the star. The data are taken on the 11th of May, 2006 with the 1m
Pay attention: Pluto is
variable during its 6.4 day rotation, so that the contrasts given below
could change a little bit.
= 100% * Star / (Pluto+Charon + Star)
Therefore, if the star is occulted, the measured intensity is
expected to drop by the approrpiate value. In case of the I Band par
example, the star signal is 45% of the sum of Pluto + Charon + star.
The contrast values have either been measured (for BVRI data) or
estimated from catalogue values (K H J Bands)
Table of contrast for Pluto
RG 695: a long path filter with a cut off wavelength of 695 nm has
been used in this case
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The weather conditions
Weather informations of the past
can be found at different websites. You can see an overview of the
global cloud coverage at the land
cloud atlas at
Other important site is http://www.ncdc.noaa.gov/oa/climateresearch.html#dandp
where you can find the "Climates of
the World" giving a lot of informations at
A commercial german website with reasonable good informations can be
You can select the country and the city. Par Example, for Tasmania ,
find the city of Hobart.
Then you get climatable with data such as max and min temperatures,
rel. humidity, rainfall, number of days with rain and sunshine hours
This may help to find out your weather for this important event. For
commercial reasons, I will not copy directly the data to this website,
you should follow the given links by yourself.
Pluto at the 12th of June, 2006
For the time of occultation (12th of June 2006) here you find
charts with different field width. They were prepared using the XEPHEM
program and the UCAC star catalogue. Some magnitudes are written to
selected field stars for information.
With higher resolution, you can downlowd finder charts with different
field sizes from the following table in postscript format:
Pluto in the
charts for Pluto in the next 3 months will be added soon.
They will show the orbit of Pluto with tickmarcks every two days
the July map, there its every day) and labels every 10 days. Each label
and tickmark has been set for 0h UTC. Postscript files you can download
from the server
as well. Charts have been prepared using the XEPHEM program and the
UCAC catalogue. These charts are to facilitate your observations for
equipment testing etc.
Here you can download the files in full resolution as postscript files, but please, it will take
some more days to finish this....
The lunar problem
As you can see from the finder chart with 50 degree field size,
the near full moon will be only about 15 degrees away from Pluto. This
is a very serious problem, what can ruin your observation, if you do
not take special precautions. Even with large telescopes you may not be
able to find and image Pluto, if scattered light gets into the
tube of your telescope. A long dew cap may be necessary to definitely
avoid direct moon light on your entrance pupil or get into the
You should test
this in the upcoming months. Try to image a faint star of about 14th to
15th mag, about 15 degrees away from the moon, take a full moon night,
if possible, or a very bright illuminated moon! Select the position
angle relative to the moon to be about the same, as during the
observing night of June 12th! And use a similar hour angle for your
For more informations and
contacts to other groups, please contact myself:
International Occultation Timing Association (IOTA-ES)
Research and Development