Pluto, Charon

From: "Torben Taustrup" <ttau@xxxxxxxxxx>
To: "Astrolist" <astrolist@xxxxxxxxxxxxx>
Date: Thu, 7 Jul 2011 08:23:49 +0200
En version med ændret linjeombrydning:


From J.Lecacheux.

 From three observatories, three chords were recorded on 
June 04  morning first across HARON, then three chords 
across PLUTO 11.4 minutes later.

 B.Sicardy pointed out :
 " This is the second double Pluto/Charon occn observed, 
after the 22 June 2008 one detected from Australia and La 
Reunion. Now, these are the very first light curves with 
BOTH Pluto and Charon occns."

 The three stations were
 -the Pico dos Dias Observatory in Brazil, alt. 1850m, where 
a fast  EM-CCD camera was used on the 1.6-m telescope by the 
Rio-de-Janeiro  team;
 -the 0.6-m remote-controlled Belgian telescope at ESO La 
Silla, alt.  2300 m, with a thinned back-illuminated CCD 
(Liège University);
 -the 0.5-m, 0.4-m (remote controlled from Spain) and 0.36-m 
telescopes  at San-Pedro de Atacama in A.Maury's private 
observatory, alt. 2400m.

 The star magnitude was expected V= 16.7, R= 16.2 from the 
catalogues and from recent CCD measurements, but fortunately 
was found a factor
 two brighter, i.e. V ~16.0, R ~15.5. So the depth of the 
six recorded events was -12 % or 0.14 magnitude, and the 
signal/noise was good.
 [Namely the Pluto+Charon+Star blended image dropped from V= 
13.87 to V= 14.01. Note that Pluto was less the 16 degrees 
from the zenith.]

 For Charon the event durations were 51 s, 48 s and 45 s 
respectively, and for the Pluto atmosphere over two minutes.

 The instantaneous Pluto-Charon separation should be deduced 
at the fantastic accuracy of 0.0001 arc second.


 Remember :  The fly-by of the Pluto + Charon + Nix + Hydra 
+ ?... system by the spacecraft "New Horizons" is expected 
on 2015 July 14.5, at 31.90 AU from Earth. Precisely 1500 
days from now !

--


Torben Taustrup
TOC Observatory homepage
http://tocobs.org
"Just do it"
Pluto, Charon

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