Stellar occultations: Pluto, June 12, 2006

P384.2 Postdictions

Compared to the reference track, based on the DE413/Plu013 JPL ephemeris and the UCAC2 catalog star position (with proper motion applied), we find, as of Sept 5, 2006, that the observed track is 10 milliarcsec (mas) West and 51 mas south of reference. Errors are less than 1 mas. Some of the difference may be due to the star's actual position relative to the reference position:
Source        RA  J2000         Dec          dra     ddec errx erry
------------ -------------- -------------   ----- ------- ---- ----
UCAC2         17:41:12.0743 -15:41:34.574       0       0   56   70
2MASS         17:41:12.0800 -15:41:34.500      82      74   60   60
UCAC2-2006    17:41:12.0768 -15:41:34.479      36      95   10   12
MITstrip_1.4  17:41:12.0791 -15:41:34.436      69     138   11    9
Bruno         17:41:12.0769 -15:41:34.485      37      89    0    0
Mimir         17:41:12.0770 -15:41:34.490      38      84   26   36
KPNO          17:41:12.0790 -15:41:34.530      67      44    8   32
dra and ddec are the offsets from the reference position in mas.
errx and erry are the quoted errors in position (and therefore
  in dra, ddec) in mas.  UCAC2 errors include propogated proper
  motion error.
UCAC2: the position from the UCAC2 catalog, our reference position.
2MASS: the position from the 2MASS catalog.
UCAC2-2006: the position remeasured with the UCAC2
  telescope in 2006, provided by Norbert Zacharias
MITstrip_1.4: the star position from prediction 1.4 of the MIT group.
Bruno: astrometry provided by Bruno Sicardy on May 10, 2006.
Mimir : our astrometry with the Mimir IR camera at Lowell, taken by 
  Leslie Young and Marc Buie (Feb) and Marc Buie alone (Apr, May), and
  analyzed by Leslie Young
KPNO : our astrometry from 5 nights in April at Kitt Peak, 
  taken by Peter Tamblyn and analyzed by Leslie Young
The UCAC2-2006, Mimir, and Bruno's astrometry are all consistent. UCAC2-2006 is East and North of the reference star. If we take UCAC2-2006 as the actual star position, this would move the shadow West by 36 mas and south by 95 mas relative to reference. Combining these, our best estimate is that Pluto is 25 mas East and 44 mas North of the reference (DE413/Plu013) ephemeris.
                                                    dra   dec  errx  erry
(Pluto - Pluto_ref)_2006jun12 - (star - star_ref)   -10   -51     1     1
star - star_ref                                      36    95    10    12
(Pluto - Pluto_ref)_2006jun12                        26    44    10    12

This could be an adjustment in either the barycenter position or the location of Pluto around the barycenter. For now we assume that the change in Pluto's position is due entirely to an adjustment in the barycenter ephemeris. The uncertainty in the motion of Pluto aroud the barycenter is dominated by uncertainty in the Pluto-Charon mass ratio. The combined uncertainty in the ephemeris adjustment applied to future events is roughly 14 mas.
                                                    dra   dec  errx  erry
(Pluto - Pluto_ref)_2006jun12                        26    44    10    12
(Pluto - Pluto_ref)_2006jun12 - (Pl - Pl_ref)_2007    0     0     8     8
(Pluto - Pluto_ref)_2007                             26    44    14    14

P384.2 Predictions

Other group's Predictions from Bruno Sicardy and Jim Elliot . As of 2006 Apr 21, these had no offset to the De413/Pl013 Pluto ephemeris.

Work in progress from our group Predictions, discussion and ongoing work by Marc Buie .

2006 May 19 Posted mail text file of Pluto position sent by Norbert Zacharias, measured with the UCAC2 telescope. 2006 Apr 25 New astrometric network using the UCAC2 telescope

From: Norbert Zacharias 
Subject: new star catalog from astrograph data
Date: Tue, 25 Apr 2006 17:44:56 -0400


Hi Leslie,

please find attached a mean position file covering the first
part of Pluto's path this year, which should include the
June 12 event.  The format is as before.  The file is sorted
by RA and contains 86460 lines (stars).  The data does not
include the earlier catalog you obtained.  We will compile
a final catalog containing all the data later this year.

Please let me know if you see any problem.


Leslie formatted this three ways: mpos.pl04s (raw file from Norbert), (RA, DEC, mag e.g. Input format for Buie's astrometry routines),and pl04s.asterr (file.line, JD, RA, DEC, mag, RAerr_mas, DECerr_mas)

P384.2 Weather

Bureau of Meteorology. Monthly rainfall totals June 2005
Last updated 2006 May 10 by Leslie Young, ,